Any EFFECTIVE 6.5td MPG mods ?

[sailun]

Has anybody made any modifications that REALLY and TRULY increased (or decreased) their MPG by 1,2,or 3 MPG ? Besides lifting yer foot.

Remove tow mirrors ? (I have the factory tow mirrors on tripods)

Modify/add/remove front air dam ? (mine is half cut-away for a plow)

Diff tires ? (M+S)

Remove bug deflector ?

Air Filter ? (currently Amsoil air filter)

Fuel Additives ?

Thanks

[moondoggie]

Good Day!

The Gear Vendors Aux. OD on my 95 pickup increased my mpg ~ 2 mpg. But, your signature says you have 3.23 gears, which is about my effective overall ratio. (BTW, how sure are you about the 3.23 ratio? I've got 3.42 gears in my Sub, & everyone has said that's the tallest they ever put in a 6.5 Sub.)

My 95 Sub is a 1500 too, but everything I've ever touched is identical to my 2500 pickup except the rear end, which is a semi-floater (the pickup is a full-floater). I just got back from a trip from Minneapolis MN to Corpus Christi TX via San Diego CA in the Sub, & got just a tick over 20 mpg, & lots of the time I was in the mountains and/or had heavy headwinds. I don't know what to tell you to do to fix your mpg, but it sure seems fixable.

I ran 5 gallons of Stanadyne Performance Formula through my 95 pickup at the recommended rate (1:500), & not only didn't see the 3-8% mpg improvement the said might/should happen, my mpg was very slightly lower. Personally, I put NO faith in fuel treatment mpg claims - most of the folks who say their mpg has increase due to a fuel treatment have no scientifically-collected data to support the claim. (If you want to flame me on this, feel free, but I'd ask you start another topic so this guy can get his mpg problem fixed here on this topic. Your flame topic will be useful to all of us, but would be more useful in a general data-collecting way.)

"Chevy should be paying us." I don't blame you for feeling this way, but I'm glad my experience has been different than yours. Both my 95's have served well; my 82 was wonderful; & my daughter's 89 is an absolute joy to drive. None have had any major problems.

"Besides lifting yer foot." It's too bad no one want to do this - it surely is the easiest way to significantly increase mpg. Part of my good mpg numbers is that I generally drive whatever the speed limit happens to be, up to 70 mph - I don't drive faster than 70.

Blessings!

[More Power]

The most effective weight loss program is the one that gets the most frowns.... Eat less and exercise more.... :o

So it is with improving fuel economy - slow down. :)

The two most important factors affecting fuel economy are driving speed (wind drag) and engine rpm (engine efficiency). The third most important is (are) the cyl head precups. All other mods mentioned here in the BB & content through the years individually and incrementally improve fuel economy.

Jim

[Dvldog8793]

Howdy
Most of the mods that I have done were in the name of power. The exception being the Gearvendor. BUT if you are running the gears you say then you really don't need a GV. The only other thing that I've done that MAY have had an honest NOTICEABLE (un-SCIENTIFICALLY-proven;-)) increase in MPG was when I made the switch to sythetic oils. I run Amsoil in both the diffs and Mobil1 atf in the trans. I did all these at the same time and I think I a gained about 1-2 mpg. I KNOW my trans temp went down by 20*. On a differnet note, you should consider the Phaser timing gear set if you are going to replace your timing set.
L8r
Conley

I know I lost MPG when I put my big open exhaust on because it sounds SOOOOO cool when I hammer it!!!

[sailun]

As always, thanks for the good info I've picked up here over the years.
I coulda swore that there used to be 3.23's listed on the Diesel Economics page, a few years ago. I also thought I saw it on the original factory sticker.

But, no matter. The brain remembers as it wants to, I guess. The rpm's at 65 mph sound about right for 3.42's, between 1800/1900.

Anyway, I've been using the Amsoil 15w40 and air filter for about 80k miles, now. Never got around to changing it in the diffs.

Never drive over 65, since dino juice went over $2.75. I also don't drive over 2100 rpms when accellerating, and I coast when I can. In fact, I know the brakes aren't dragging, cuz this wagon will roll forever.

In fact, I drive pretty gently, because I got so tired of paying for brakes.

Not much I can do about the pre-cup size.

When everyone changed their TDC Offset to -1.94, did you see any measurable MPG increase ?
Cleaning out the kitty litter ?
Replacing Timing chain, or gear drive ?
I'm thinking about how I'm gonna streamline these big towing mirrors, pull off the bug shield, and replace the air dam.
And change out the diff and tranny fluids, as advised.

Please post any more suggestions you have.
I'll try to keep track of any changes I detect, but the weather has just turned colder, and I'm sure all the tanks have winter mix in them now.
MPG always seemed to drop off in the winter.

Thanks.

[sidehackbob]

Don't get in a big huff to remove the air dam. It is your friend, it is there to move air smoothly under your rig at speed. It helps the Engine compartment air to flow out under the truck. It keeps wind off the steering wheels and makes for a more pleasant ride.
Maybe the cam isnt timed right in your rig, maybe its got a muffler thats colapsed inside. Does it ever run cold or does it always heat right up?

[sailun]

Sorry, sidehack, I mis-communicated there.

There was a plow with the truck when I bot it at 11k miles, and they cut away the middle 50% of the air dam to fit plow and sub-frame. I want to re-place the air dam, cuz I've heard it does good things for the truck and mileage. I figure GM wouldn't have put it there without some perceived benefit.

A 93" FLH ? Sounds like I need one of those.

[moondoggie]

Good Day!

"MPG always seemed to drop off in the winter."
If your fuel is winter-blended, your mpg will drop - #1 has (I think) 10% or so less energy per gallon than #2. I don't know what you have for fuel in CT, but here in MN I've been told there are two suppliers of diesel: Conoco, & the Coke Refinery south of St. Paul. Conoco blends to suit the weather, or the station will have both #2 & #1 pumps. The Coke refinery supplies #2 treated with something from Koch (?) that makes #2 work A-OK down to at least -40F. I was REAL leery of the Koch additive, but I've never had a jell since they started using it, so I guess it's OK.
Every bearing has lubricant that will be thicker until warmed by use.
Your tranny fluid - same story.
Your idle speed is a little higher until the coolant warms. Tiny effect, but additive to the problem.
Blessings!
(signature in previous post)

[TurboDiverArt]

Don't get in a big huff to remove the air dam. It is your friend, it is there to move air smoothly under your rig at speed. It helps the Engine compartment air to flow out under the truck. It keeps wind off the steering wheels and makes for a more pleasant ride.
Maybe the cam isnt timed right in your rig, maybe its got a muffler thats colapsed inside. Does it ever run cold or does it always heat right up?
I didn

[sailun]

That's what I wanted to hear, some real results.

Gives me a good place to start working from.

Thanks, everybody. Keep posting any items that you found produced (or did not) a significant change.

Which specific gear and tranny lubes were used ?

Answers to other questions: Yes, it seems to warm up OK, especially when I seem to have to replace the t-stat every 2 or 3 years. Bot the truck in '01,
put the 2nd replacement t-stat in this past spring. Stock 180 degree.

Gearing: 65 mph = just about 1800 rpm. tires are Cooper Discoverer M+S 245's, new this year, lot's of tread.

[moondoggie]

Good Day!

"Stock 180 degree." Actually, stock is probably 195F. You might want to verify this - mpg will be a bit better at 195 than at 180.

Blessings!
(signature in previous post)

[sailun]

I'm sure you're right, Moondoggie. When fully warmed up, the gauge says 190 (halfway between the 160 and 210), or just a tick under. I did try briefly to find a 200 or 205 deg t-stat once, for a little more heat. No luck,

Also, tach says 1800 rmps, right on the button, @65 mph.

Of course, I'm sure there's a little bit of error to be found in these fine, precision instruments.

Bought a new clamp for the cat/muffler joint today, probably try to separate the two, and clean out the cat tomorrow.

What's everyone's preferred tool for this job ? I'm guessing that a toothbrush taped to a popsicle stick isn't gonna do it.

Kevin

[Mark Rinker]

My preferred tool for 'cleaning out a cat' is a chunk of 3/4" rod. Secure the cat in a bench vise, then jam the rod in one end with great force, until you hit resistance. Keep jamming and banging away, pulling out 'peices of soot' until you can see clear daylight from end to end. A rubber mallet may come in handy.

Then re-install your 'cleaned out cat'.

:)

[sailun]

I found a long 5/8 masonry bit works really well. Also, I modified the end of one of those paint mixers (5 gal pail size) you chuck in a drill, and that tears it up pretty good.

BTW, I did not remove the cat from the truck. I removed the clamp, and cut between the cat and muffler with the Sawzall, and muffler drops down out of the way. Easy access for drilling. Shop Vac hose fits right into the cat. Muffler slides right back on to the cat when you're done, and crank down on a new clamp.

No welding !

Sure seems to drive perkier.

I'll post with results after a few tanks. There's gotta be some kind of measurable improvement, after removing that kind of a restriction.

Thanks, Kevin

[Scooby]

Using a synthetic will give the best protection, and also the best mileage with the proper weight oil. I use Amsoil in everything. It is good stuff, and when you factor in the longer service life, really isnt more $$.

My 2 cents.

[TurboDiverArt]

Using a synthetic will give the best protection, and also the best mileage with the proper weight oil. I use Amsoil in everything. It is good stuff, and when you factor in the longer service life, really isnt more $$.

My 2 cents.
I don't know, I'm just old school I guess. I never leave oil in anything past 2500-3000 miles. I'm not so much worried about it breaking down as I am about it being dirty and the filter not being able to keep it really clean. Even with a small micron synthetic filter diesel oils get a lot of soot build up. Maybe with ULSD the oil won't be as black and I would be OK with leaving synthetic it in longer. I typically change oil on average every 2-months so it can get pretty pricey with synthetic if I can't convince myself to leave it in there longer.

Art.

[sailun]

Update. 16.1 mpg on the first half tank (20.4 gals, 330 miles). At most, half of that was highway @ 65, the other half never loks up the Torque converter.
Can't tell the net change yet, could be .5 MPG, could be 1.5 mpg.

What's even more impressive is the difference in power. I have no way to measure it, but I am still re-training my right foot to push down less. I just push down to 1800 rpms, and she just pulls right up through all the shifts.

After unclogging the cat, and seeing the huge difference it made, I've been looking around under the hood to find a way to get to some cold air. We have great big air filters, and little tiny air passages. I am amazed at the restrictions our intake air goes thru. The snorkel behind the headlight, up to the fender, seems very restrictive something like a 1" by 3" opening, then a small 3" circular vent from the fender to the airbox. Seems like only a 3" diameter circle of the air filter is used. Then squeezed again between the airbox and the bellows into the turbo.

I haven't found a better air routing, so yesterday I just took the lid off the airbox. Amsoil filter inside. Yes it sucks warm air, but it sucks a lot easier, over the entire filter. Maybe I'll have to put it back on in the summer, but it feels fine, for now.

SSDiesel has a nice-looking intake & filter, but I'm cheap. And, their set-up pulls warm air, also. In fact, almost any aftermarket intake-filter for any street vehicle pulls warm air.

So far my MPG quest has cost me a $3.00 clamp, and a used Sawzall blade.

Synthetic oils: I'm a believer, been using it for at least 80k miles, especially when you shut off a hot motor and the oil just sits in the turbo bearing. The motor gets a lot quieter when I change it after 7000 miles. 6000 might be a better interval. Who makes the "Best" oil filters ? Any consensus ?

Thanks for everyone's help, please keep the advice coming. And show me pix of your trick intake set-ups, and any perceived results.

Kevin

[Dvldog8793]

Howdy
One of the easiest/cheapest things to do for your intake is to get rid of the plastic snorkel. Next would be the air path from the turbo to the intake. John Keneddys web sight used to have good pictures of this. The next thing I would do is remove the EGR system, if you have one. I did this on my 1984 van and it made a noticeable difference. That might take some money as I think you have to get a new intake.
Spend some money on a new "un-adjusted" down pipe. The down pipe on the turbo is probably the 2cnd biggest source of restriction. Then if you really want to change things out get a big exhaust or at least open up the factory system even more. The list goes on on on on on ..... How much money can you spend!
I am a big believer in the benifits of synthetic oils in COLD environments. I use Mobile Delvac1 in the winter and Delvac 1300(regular) in the summer. It has been discussed and argued MANY times about going long change intervals with synthetic in a diesel. The main problem is the soot/abrasives that build up in the oil. I run a Amsoil dual filter/bypass filter with the biggest filters I can get. I still change my oil and the regular filter ever 4000-4500 miles. In the summer with regular oil and higher temps I change every2500-3000, sometimes sooner if I get my oil temps up high on a load. I use WixPremium filters but I have also heard good things about Donaldson(I use them in my equipment) and Hastings. I think Napa Gold and CarQuest Premium are both Wix filters. I have heard bad things about the orange brand (and have taken them apart in my lathe) and would stay away from them.
Hope this helps....
L8r
Conley

[TurboDiverArt]

I use WIX filters. I buy them by the case from FleetFilters.com who are supporters of this site. You get them in NAPA Gold boxes at about 1/2 the price. I was using Baldwin filters before, probably one of the best filters out there but they are like 3-times the cost of a WIX. Since I change my oil every 2500 miles I'm not too worried about it. I'm hoping with my next oil change that the oil is less sticky now with the switch to ULSD.

Art.

[sturgeon-phish]

I don't think your '97 has a snorkel. I agree there is not much of a free flow air path so I modified the air intake route. I removed the turn signal lens, installed an after market turn signal, keep both lights to keep the turnsignals operating properly, on a homemade braket screwed to the inside support then mounted the new turnsignals. Then I took the sheet metal from an old computer, but any metal with lots of holes for air circulation, and cut it to fit the opening for the turnsignal housing and use the existing screw holes to hold it in place. Repeated for the other side. Cost around $20. I did see an improvement in MPG.
As with other posts I agree that the synthetic oil and trans fluid and opening the exhaust are the biggest non-driver related improvments to better MPG.
Jim

[Tim Pringle]

Just a comment or two: From my own experiance, after market bug deflectors & rear window air deflectors (Suburban) do seem to help keep the windows cleaner, but at a price of about 2mpg each. I decided a squeegee was more economical.

Winter blend fuel has less punch - I found (I'll probably get reamed for this - but) adding a quart of drain oil to each fill up seems to correct this. I myself usually add a quart reqardless, 2 if I feel the fuel is 'weak'. It raises the btu's, lubes the pump & ups power. My '82 loved it - I could tell by the seat of my pants if I had oil in the fuel or not. Lighter weights dont smoke, heavier weights smoke more. Dont use gear lube or synthetics, they wont burn.

Fresh injectors help, for awhile. Abuse it once in awhile. Diesels load up when 'babied', and you need to flog it forthrightly once in a while to make a plume of smoke that will block out the sun!

Have fun!

Tim

[sailun]

Thanks, Tim. I'm gonna burn off a few tanks before I remove the bug deflector, just to see if it makes a diff.

Darn, I can't burn all this dirty drained Amsoil ? Guess I'll go see what's on sale. Hey, if it's under 72 cents/quart, it's cheaper than diesel.

Changed fuel filter yesterday, looks like it has been awhile. I bet that helps too.

Also extended the filter drain hose, so I can collect it in a jar, instead of washing the oil off the engine & suspension onto the driveway. What would another foot of hose have cost the factory ?

I bet no one else knew that the hoses on the drain valve are not plumbed the way logical minds might do so. Nope.

The hose that looks like it comes from the fuel filter, does not. It is the overboard drain hose. The hose that points down towards the ground is not the drain hose. It is the line from the filter. Do not cut this line off the fitting as you are proceeding with your plan to extend the drain hose.

To re-iterate, the line draining water/dirt/fuel from the filter is attached to the BOTTOM of the drain valve, and the drain line going to the driveway is attached to the TOP of the drain valve. So fuel plows UP thru the valve.

Upon reflection, the valve is mounted upside down, so we can actually use it to spray fuel all over the vehicle and driveway.

Sorry about writing a book, too much time wasted splicing hose back together.

[sailun]

Are all the cat's this clogged ? Unbelievable. 50% of the tubes that aren't clogged on the end-grain, are clogged inside.

This '97 only had 11k miles on it when I bot it in 2001, so I'm guessin this was caused by condensation, and lack of use. Or do they all look like this ?

Pic: http://www.thedieselpageforums.com/photopost/data/500/medium/Cutdown.JPG

[sturgeon-phish]

When I cleaned out my cat I had 65K and it was pretty plugged. Removing the media made a big difference in fuel consumption.
Jim

[TurboDiverArt]

Mined looked like yours after 120K. Made a huge difference in both performance and mileage.

Art.

[sailun]

OK, second haffa-tank. 401 miles, 25.8 gals. 15.5 mpg. At most, 80 miles of highway driving. lots of around town and Christmas shopping traffic driving. I figure it's up one mpg, around town. I'm happy with that. Highway mpg, and money-intensive improvements have to wait till I'm working again.

Anyone have a leaking rear-door seal on their 'Burb, and any luck fixing it ?
I laid in some RTV under the third-brake light on the roof, so that wasn't it.
Also found an original srvice record, original owner had the seal sealed again at the dealer.

Also a leak from under the dash/heater, soaking the carpet on front passenger side ? I sealed a few screwholes under the black plastic cowl grill, but the carpet's damp again. It's definitely rain water, not heater water. Doesn't stink or smell like A/F.

The large opening in center of cowl, behind firewall. Where does that go, (climate control intake ?), does it have a drain that might be blocked up ?

Happy New Year.

[sailun]

Went up to New Hampshire and Vermont for cheddar cheese and real maple syrup. If you think synthetic oil is expensive, you should try maple syrup at $24/qt.

Only a 200 mile trip, but real improvement.

17.9 mpg @ 70 mph

only real mods so far were opening up cat, and removing Lund bug deflector.
And adding some two-cycle oil to each tank.

New synthetic lubes go in the diffs and tranny this week, along with injectors, timing chain.

New exhaust, too, if it gets here in time.

[sailun]

Hwy MPG now usually 17.5 to 17.9 , cruise control, 68-70 mph

Haven't been doing many long trips, or commuting, so no statistically valid numbers, here.

But, considering I was at 14.5/15/15.5, never 16, hitting mid-to-high 17's is AOK.

Mods so far: all Synth lubes. cleaned out cat, then installed 3.5 KD exhaust (very nice power bump, especially highway passing !) removed bug deflector, no lid on the air box.

Didn't get to do timing chain or injectors, yet.

[moondoggie]

Good Day!

Good progress! If 15 to 17.5 doesn't impress you, take a different look at the numbers. At $2.60/gal of fuel, you're now spending $2.48 LESS per 100 miles driven. That's pretty significant - you're using almost 1 gallon less to go that 100 miles.

Blessings!
(signature in previous post)

[JTodd]

I have been putting a bunch of miles on my Sub lately (more than 1200 miles a week), and have become keenly interested in improving my fuel mileage. I have done some simple things and have seen my mileage improve from 16.5 to 18. I hope that with summer blend fuel and a couple more 'tweaks' I might get closer to 19.

I have not done anything major or expensive -
*Removed the snorkle and keep the air filter clean - Free
*Replaced the front indicator light with a piece of pierced metal screen - Free
*Removed the wind deflector on the hood - Free
(Even though it is one of the contoured ones, it seems to make a difference.)
*Straight piped front to back, no muffler or cat - $15 for the pipe
*Went with 195* thermostats - $28 and they needed to be replaced anyway
*Keep tires inflated to optimal - Free

The biggest thing, though is keeping out of the throttle. I cruise at between 72 and 75. MPG really drops when I get to 75 and above. I might see an increase with new air cleaner assembly, new down pipe and synthetics, but not bad. Just food for thought.

[moondoggie]

Good Day!

You oughta see what happens when you get down to the speed limit. In Nov 06 I drove our Sub from Minneapolis MN to Corpus Christi TX via San Diego CA. I averaged 20.3 mph for the trip; worst tank was 17.1 from Oklahoma City OK to Des Moines IA (my notes say "25-35 mph headwinds gusting to 60 mph; 4-6 # boost to maintain 70 mph (usually only 3 #)); best tank was 23.1 from Flagstaff AZ to El Centro CA - I even ran the A/C ~ 1/2 the time on this leg! (My odo checks out < 1/2% error against the mile markers in several states & many highways.)

The only mods to my Sub are JK's exhaust & TDCO set to -1.94 a couple years ago when John installed the exhaust system. BTW, it has 3.42 gears.

Nobody wants to do it, but the simplest way to get better mpg is to slow down. ;) I drove the speed limit up to 70; when the limit was > 70, I drove 70.

Blessings!

[JTodd]

I have 3.73 gears. and you are correct, the best savings is from slowing down. It makes the trip cheaper, but longer.

[sailun]

Nice mpg, esp. w/ 3.73's.

most recent haffa tank was 17 mpg, about half @ 70, half stop and go.

I gotta think I'll be 18+ on a trip.

I'm trying to figure out another way to get cold air into the airbox, I'm thinking a deflector of some kind, versus the perf metal. I'm closing the airbox back up, I've been running with it open.

I'm pretty sure there's a front-end alignment in my future, I'm sure that will help.

I'm also pretty sure that my factory tow mirrors, with their big tripods, might be costing me quite a bit.

[sailun]

Went up north for BBQ ribs this weekend. 197 miles round trip. When I re-filled, put in 9.76 gals. 20.18 MPG. Cruise control at 70 mph.

I know this is nowhere close to a statistically valid sample, but is sure is an encouraging sign.

In my normal commuting, (half highway, half 40 mph parade) and driving kids around, I'm usually getting 16.5 to 17 MPG.

Mods so far :

KD 3.5" exhaust, clean cat.

new injectors,

all synthetic lubes,

"ram-air" turn signal light. Well, it lets in more cold air than stock.

Air box has been closed back up for weeks, to get the cold-air only.

Removed low-profile Lund bug deflector.

Power Supply Cetane boost (I'm addicted to this stuff !)

Replaced missing portion of front air dam with a thin piece of maple, painted black. (This made a HUGE improvement in highway handling. My front end is loose, but this really quieted things down, especially on gusty days).

Big change from when I was getting 14.5 to 15.5, NEVER getting 16. Between +1.5 to +2.0 mpg around town. Maybe +4 on long trips.

Also, I'm thinkin' maybe the service stations have switched from #1 to #2 recently.

[moondoggie]

Good Day!

Going from 16 to 20 mpg may not sound like much, but it might sound better if you invert your thinking.

mpg is a useful term if you're allotted a certain # of gallons, & the goal is to make the most miles out of it. Fortunately, that's not the situation for most of us. We decide on our trip(s), then buy whatever fuel is necessary to make them. So, I tend to invert mpg & look instead at how many gallons I'll need per 100 miles.

16 mpg = 6.25 g/100m; 20 mpg = 5.00 g/100m. So, you've saved more than a gallon every 100 miles you drive. Do the math: it's pretty significant.


Blessings!
(signature in previous post)

[sailun]

It's significant, all right !

You can bet I was pretty stunned when the pump read less than 10 gallons, and I couldn't squeeze any more in !

I don't really get to do any long, full-tank or multi-tank trips, and commuting traffic varies from day-to-day, so I'm probly never going to get any rock-solid, repeatable MPG numbers.

But I'm happy with the results so far.

Now, how to get the next 10 % increase ...............

Stream-line the mirrors ? remove the roof rack ? build a front bumper like a Kenworth, or a new Silverado ? (Hey, they already did the aero research, why not take advantage of it ?)

Hey, where's the 30 MPG Diesel Camino, anyway ? Surgery finished yet ?
Moving under it's own power ?