Oil 'blow', K&N air filters, and gas mileage....

[pitroad]

I have an '06 DMax LBZ with 36500 miles. I've owned the truck for approx. a year and have put about 13K on it. About a week ago, I changed the stock air filter out to a K&N. During that change I noticed what appeared to be oil that looked like it had been blown at some time on the left side of the engine compartment. Mostly on the hoses off to the left of the motor, and not any on the motor itself. I pulled the entire air filter housing out to check further, and was soon needing to replace my fuel filter so I pulled the inner fender off to get a better look. It seemed to be dried oil/road gum that seemed like something had built up pressure and blowed oil. It even appeared to run out that side of the fender when it happened. I park the same place at home and at work and haven't noticed any leakage. I took the truck to the local dealership the next day and let them look at it. The first thing the tech did was pull the air filter top off and ask me how long I had this K&N filter in. I told him I just installed it the day before. He told me that GM recommends not using K&N filters because they are oil-based filters and messes with the air/fuel mixture into the engine. He also told me that the engine would be getting too much air. I questioned this and explained that I had NEVER heard of an engine getting too much air, that I always had been under the impression that the more air the better. He said that in the past this was true, but with these new more sophisticated motors, they were tuned for the exact amount of air, etc. At this time he also noticed that I was missing the air filter gauge that protrudes out of the filter housing and said this too might be causing the motor to get too much air and this is what probably caused the turbo to possibly build up pressure and blow this oil back out.
I also questioned the dealer about the gas mileage I was getting and had there been any tech bulletins concerning poor gas mileage. I explained to him that I drive highway miles back and forth to work at 55-60 mph, and regardless of pampering the DMax or driving the fool out of it, I'm luck to get 16 mpg. I told him that I pulled a 30' RV which didn't weigh any more than 7-8K and was VERY lucky to get 10 mpg when towing. He said he didn't have an answer for me, but would research it before I p/u the air filter gauge part they ordered.
Well, I questioned with friends who own DMax's and they all told me the too much air was 'hog-wash' along with the K&N story he told me. I changed out the fuel filter a couple of days ago, and haven't noticed any more oil anywhere.
I went and p/u the air filter guage part that came in today, and also questioned about whether they had found any thing about the fuel mileage I was getting and he pretty much just blowed me off, telling me that there weren't any bulletins out and that's just the way certain vehicles were.
Should I be worried about the oil 'blow' issue? Does anyone else know anything about the too much air comment I was told? What about using K&N air filters? And am I complaining about my gas mileage?

Thanks in advance!

[Mark Rinker]

Only a moment to respond, so here are my thoughts:


OEM paper filter is best for diesels, changed often. However, your problem was there before the filter, so discount dealership/turbo warnings. Do not over-oil, or oil both sides of your K&N it will screw with your MAF sensor.
Sounds like a leak from your A/C system. Does A/C function normally?
My '06 mileage is the lowest of all 5 DMaxes owned. About what you describe.
Do fuel filters every 10-15K, use synthetics in rear diff, slow down and no extended warm-ups or idling to conserve fuel.

[More Power]

I read in a recent diesel publication where K&N was asked about MAF sensor fouling, dealer complaints and warranty denials as a result of using their oiled-gauze air filters. K&N, in the article, tested several dozen of current truck air induction systems and MAF sensors, and found that K&N was not blame for nearly all diagnosed problems. K&N went further in asking owners who use their filters to contact them when/if they experience any difficulty in obtaining warranty service. According to the article, they are prepared to back you up with engineering support and scientific research in defending your warranty.

Just thought I'd pass that along....

Jim

[pitroad]

I'll keep that in mind.

[DickWells]

Just for WIW, I'd talk to another dealer. You didn't say where you live, but you can find good, reputable GM places by researching it right here on the DP. I can tell you who to talk to in S. WA, S. TX, W. Central FL, W. Cent UT, and N. Cent, VT, but that's probably of no help to you. I seem to remember that there was a DP feature dedicated to recommended dealers a few years back. Regardless, the tech you talked to didn't give any concideration to the fact that you had blown oil showing when you put in the KN. Some of these dealer people talk like there isn't another inteligent person in the country!
I have a KN in my old 95 Burb 6.5 that's got 80k+ on it, with no problems. I was so concerned over the horror stories that I heard after I put it in, that I wrote to KN. Got a good, long letter back that didn't do much to make me feel better, but time and mileage proved that what they said was right.
I have an S&B in my GMC, that's been there for about 25K. Again, no problems. Had a guy in our caravan to AK and back last summer who kept changing his factory filter in his 06 DM, because his mileage kept going away. Claimed he gained 3 mpg (towing 5th wheel) every time he put in a new one. I got 13.2 for the 8 weeks and 7+K miles, and had cleaned and oiled it before I left OR. I cleaned it again in VT last Christmas. That's it.
Good luck with your DM, hope you learn to like it as much as I do mine.
Dick Wells:)

[Dakster]

Pitroad - I get about 16 on the highway in my 07.5. I don't pull enough weight to compare, but I did get 14.5 pulling a 4k cherry picker at 65 mph.

The best mileage I got (according to the DIC - which is usually within .25 of my hand calc) was 19.0 driving 45 mph up and back to the florida keys. No stop lights for the 100+ miles I drove and I only made one stop - turned around and drove back. The motor did not even have enough time to cool off for the stop.