Fuel Mileage

[JTodd]

What kind of fuel mileage are members of the page getting?

My 2500 4x4 Suburban averages between 16 and 17 mpg. That is with 3.73 gears, a lot of commuting miles (read: mostly highway and running without a load) and a very soft foot (rarely over 2200 rpm and highway speeds around 65 to 70, which is around 2000 rpm).

It would seem that I should be getting a couple mpg better. Air filter was replaced recently and currently runs stock exhaust. It fires up very quickly and easily, so no outward evidence of bad injectors or compression issues. Any ideas on improving mileage? I would imagine that upgrading exhaust and intake would improve both power and mileage - any body track this?

[moondoggie]

Good Day!

You might want to look at my post in What's your fuel mileage with a load? (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=004439#000014) (Click in colored text.) This subject comes up with great regularity. You might want to try the search feature too. ;)

Blessings!

Brian Johnson, #5044

[Perry]

Your Suburban's mpg seems pretty much correct at least based on my experience. I've watched this page's postings for many years and have always been amazed by other 6.5's fuel mileage.

I've tracked my mpg for 5 years on my bone stock 3.73 Suburban, and I've averaged 13.5 mpg driving a equal mix of highway and city. Roadtrips were usually 16-17mpg going 70-75mph. I just figured my mileage was lower due to the hilly terrain that I drive in the Pacific NW.

I just put on a new downpipe and free flow exhaust last month and my MPG was still 13.5. One tank can't really provide accurate data, but I did use my right foot more as I like hearing the turbo whine.

I just installed Bill Heath's new ECM upgrade last weekend and will be taking a 250 mile trip tomorrow. It will only be based on one fillup, but I'll let you know if my highway MPG is any different.

Perry

[triggerman]

Yep, your right in the ball park. I'm convinced their isn't much you can do to up your numbers. I have always felt the IFS auto hubs kill a good 1 or 2 mpg's on these trucks. Some day I will prove it with some creative tinkering ! ;)

[AC Bingel]

I get about 15 mpg around town and 18-20 on a trip. I also have 3.73. I like to drive fast so my mileage is not as good as it could be. I Just installed 3.5" exhaust all the way back with no cat but have'nt checked the mileage yet. From what I have read on this site it should help with the mileage

[TurboDiverArt]

Originally posted by Perry:
Your Suburban's mpg seems pretty much correct at least based on my experience. I've watched this page's postings for many years and have always been amazed by other 6.5's fuel mileage.

I've tracked my mpg for 5 years on my bone stock 3.73 Suburban, and I've averaged 13.5 mpg driving a equal mix of highway and city. Roadtrips were usually 16-17mpg going 70-75mph. I just figured my mileage was lower due to the hilly terrain that I drive in the Pacific NW.

I just put on a new downpipe and free flow exhaust last month and my MPG was still 13.5. One tank can't really provide accurate data, but I did use my right foot more as I like hearing the turbo whine.

I just installed Bill Heath's new ECM upgrade last weekend and will be taking a 250 mile trip tomorrow. It will only be based on one fillup, but I'll let you know if my highway MPG is any different.

Perry Ohh, a 99 burb owner that's trying out Bill

[catmandoo]

are the 1500 subs geared any better then the 2500.i've been looking for a 94-up sub and i want over 20mpg for sure to justify the purchase of it.,i don't haul anything but people and i would probably never tow a trailer with it.and i myself would prefer a 2wd but momma wants 4wd for the winter so looks like it'll be a 4wd.my current 2wd pickup runs on average 25mpg and it's 95 percent highway miles at 65.

[Polar Diesel]

my 93 with 4:10's will get 16-16.5 at 65mph with stock tires. I put 285s on and it think it helps the milege. it helps the gear ratio on the hiway. at 55 the speedo indicates 1900rrr's in overdrive. and about 2500rrr's at 75!!

[moondoggie]

Good Day!

My 95 2500 pickup has 4.10 gears, my 95 1500 Sub has 3.42 gears. For the differences between 1500 & 2500 Subs, you might want to look at Diesel Suburban Facts. (http://www.dieselsuburbans.com/DieselSuburbanFacts.htm) (Click in colored text.) Scroll down to "Differences between the 1500HD and the 2500."

For the difference gearing can make, see my post of 5 May.

Blessings!

Brian Johnson, #5044

[Perry]

Art,

The heath ECM made my 99 Suburban come alive. I didn't know that the 99's came with HO programming, based on how it used to drive, it sure didn't seem high performance. According to the sticker on the aircleaner, my 99 is rated at 195hp, which i thought was the same for the other L65's.

The new ECM gives me more power everywhere. I drive mostly in town and in traffic, but even when going slow in town or climbing hills at 35mph, the Suburban does it with authority. And when using the accelerator pedal aggressively while accelerating from standstill or up a hill or onto the highway, it feels like I swapped out for a 454.

And MPG stayed the same. On my 250 mile trip yesterday, I had 17mpg on the fillup, which was the same as it was stock. But now there is a lot more power to easily climb up hills at 65mph, and I don't hold my breath passing people on 2 lane hwys, so its kinda nice to have more power without sacrificing economy. I was hoping for better MPG, as this morning when I topped of, fuel is now $2.03/gal which is almost 10 cents more per gallon from the beginning of the week.

Perry

[TurboDiverArt]

Perry,

I think the 98 and before diesels are 190HP and 395 ft/lbs. The HO program is 195HP and 430 ft/lbs. That

[Perry]

My 99 still has the stock injectors. According to Bill, he stated that I should expect at least 205 hp and 510 ftlb torque at the rear wheels with the ECM and exhaust. One of these days when my other car club has their dyno days, I may just bring the Sub to confirm, but based on how good it feels driving, the actual numbers don't really matter.

When I had the new exhaust put on, they welded and capped the pyrometer bunge before installation. Since I had the exhaust shop that actually makes the exhaust for Heath handle the install, they had to weld the cat back in.

And for the boost, I was going to tap the manifold, but its been suggested to take the factory temp probe out and using that location for the boost. I would just need to insulate the loose probe from the engine compartment heat.

Where do you have your x-monitor on the dash? Did you think about putting it on the steering column?

Perry

[TurboDiverArt]

Originally posted by Perry:
My 99 still has the stock injectors. According to Bill, he stated that I should expect at least 205 hp and 510 ftlb torque at the rear wheels with the ECM and exhaust. One of these days when my other car club has their dyno days, I may just bring the Sub to confirm, but based on how good it feels driving, the actual numbers don't really matter.

When I had the new exhaust put on, they welded and capped the pyrometer bunge before installation. Since I had the exhaust shop that actually makes the exhaust for Heath handle the install, they had to weld the cat back in.

And for the boost, I was going to tap the manifold, but its been suggested to take the factory temp probe out and using that location for the boost. I would just need to insulate the loose probe from the engine compartment heat.

Where do you have your x-monitor on the dash? Did you think about putting it on the steering column?

Perry I thought the ECM needed the temp probe?

It's good to hear that you are that pleased with the performance of the ECM upgrade. Seems like the best bang for the buck!

My X-Monitor is mounted above the radio. I didn't want it on the left side for people passing by the truck to see it. Besides, that way the passengers can see it! smile.gif

Based on my own experience. I picked up 1.5 MPG when I "cleaned out" the CAT. The truck also seemed to be peppier. I bet by cleaning out the trap you would notice a difference. Also nice to hear that even with stock injectors you notice a good difference.

Thanks for the info, I'm sold!
Art.

[tswartos]

I have the same gear ratio...your best mileage will be when u keep the RPMs in the 1800 range. I read it in a posting some time ago that also had a spreadsheet accompanying it...I believe its in the members area. It was a basic breakdown of tire sizes and rpm levels. That bit of info goes a long way in understanding how to drive the 6.5...once I figured it out, i was controlling my mpg instead of crabbing about it. I increased my tire size and backed my foot out of the gas pedal...that meant 16 mpg in town and 20 plus on trips. Now...if I dont feel like taking my time, I take a mpg hit and drop to 14mpg city/ 16mpg hwy while generally running at 2200 RPMs