2015 Sierra 1500 5.3 UOA with high fuel dilution

[LDM]

Long time lurker, first time poster. I bought this truck in December 2017 with 20K miles, this is the first oil change and I had a UOA done to see what the oil was like since I had no idea what was put in or when. I assume it was 0w20 ACDelco as I purchased the truck from a GMC dealership. Oil filter was an AC Delco PF-63E. The fuel dilution is over 10% and below grade according to the info. The suggestion is to get the fuel system checked but I find this odd as the truck does not get poor fuel mileage (sure gets a lot better than the 95 Tahoe that I had before this). I also did not notice any increase on the dipstick, which I check at least once a month. Never had to add any oil during the 4K miles that I put on the truck either.

Just looking for any further suggestions on the data here. The iron and copper are a bit higher than normal wear according to the lab. The truck is still under warranty so I could take it in and have everything checked without any cost other than a bit of my time. Truck runs great and I haven't had any issues during the last year of ownership. This is my first newer vehicle in quite a while, I also have a couple of older Camaros that I enjoy when its nice out. I do have a very short trip for work, I only live a couple of miles away so the truck rarely gets up to temp during this 5 minute drive. However, I do take it on longer drives at least once a week where it does get up to temp and do the occasional hauling and towing when needed. Any info for those who are more familiar with UOAs would be appreciated, I know a lot about cars but never used a UOA before. I figured since the first 2 oil changes came with truck truck from the dealership that I might as well see what info I would get from a UOA.

 

[dishdude]

With that amount of fuel, I'd think you would see an increase on the dipstick. I'd take another sample at around the 2k mark and see if fuel is elevated.

 

[PimTac]

It might be prudent to get it looked at, especially the fuel injection system.

 

[clinebarger]

Vehicles on the sales lot get moved around, Multiple times a day in some cases. Even if the oil was changed before being put on sale.....It could of had 100 short trips before it was sold to you?

Change the oil & retest!!

 

[anndel]

Maybe engine blow-by could be another cause of excessive fuel in the oil. Do a compression test of each cylinder.

 

[rubberchicken]

I would take it back to the dealer, and complain somehow. If its noted in the official history, and something goes wrong when out of warranty, then you have some recourse. Any check engine lights or codes you can blame it on ?

 

[claluja]

Delete - double post.

 

[claluja]

My recommendation is do a short OCI of 4K miles, sample again at that time and send to a lab that uses gas chromatography to measure fuel dilution. Blackstone numbers could easily be wrong, as Blackstone doesn't actually measure fuel dilution.

And keep a close eye and nose on your dipstick, to see if it rises at all or smells like fuel. If you have over 5% fuel dilution, you should be able to smell gas on the dipstick.

 

[SteveSRT8]

Despite all the excitement over extrapolated fuel dilution numbers there has been virtually nothing posted about real world damages.

 

[PimTac]

Originally Posted by SteveSRT8
Despite all the excitement over extrapolated fuel dilution numbers there has been virtually nothing posted about real world damages.





True but 10% fuel dilution is a sign of something awry. I do agree though that UOAs with fuel dilution in the 2-5% range have not shown higher wear metal accounts.

It should be noted though that we are only seeing snapshots and not trends.

 

[SteveSRT8]

Originally Posted by PimTac
Originally Posted by SteveSRT8
Despite all the excitement over extrapolated fuel dilution numbers there has been virtually nothing posted about real world damages.





True but 10% fuel dilution is a sign of something awry. I do agree though that UOAs with fuel dilution in the 2-5% range have not shown higher wear metal accounts.

It should be noted though that we are only seeing snapshots and not trends.



Absolutely, and a good point as most of us know. One UOA rarely tells the whole story.


I have owned many higher performing cars over nearly 50 years and fuel dilution is one of the things I have always had to pay attention to. My sig car almost always has some significant fuel dilution and that is why it is factory recommended for a 3000 mile interval.


Neither myself or my BIL who is a 3rd gen machinist with decades of HiPo engine building experience have ever heard of any engine with damage from fuel dilution.

 

[LDM]

Thank you all for the replies. I may do a compression test just to check, although the truck runs fine and there are no issues that I can tell. No SES lights or anything of that nature. Maybe this weekend I will hook up my OBD2 data logger and get some engine data as well, see if I can spot anything. When I took the sample for Blackstone I did not notice any gas smell in the oil, which is another reason I found the high fuel dilution to be odd. At 10%+, it should definitely smell like gas.

And 4K miles is only what I put on the truck after I bought it, no idea when the oil was changed before that. It was a fairly cold winter here in IL last winter, I did do some remote starts and let the truck warm up before going places during Jan-Mar months. I almost certainly will do another 4K interval, just to make sure to have a similar comparison. That will probably take another 10 months as I don't do a lot of long distance driving anymore. I also plan on checking the oil more often, probably at least once a week now, just to see if I can notice any change in oil level.

 

[PimTac]

Something to think about here, Blackstone is known by members here to be inaccurate in their measurements of fuel dilution. The process they use is not accurate. Their reports tend to underreport fuel dilution rather than over.

I might give them a call and see if they can rerun the fuel dilution part of the test. They keep oil samples for a period of time just for this.

 

[OVERKILL]

Originally Posted by PimTac
Something to think about here, Blackstone is known by members here to be inaccurate in their measurements of fuel dilution. The process they use is not accurate. Their reports tend to underreport fuel dilution rather than over.

I might give them a call and see if they can rerun the fuel dilution part of the test. They keep oil samples for a period of time just for this.


With a flashpoint at 275, I'd say the 10% figure is, if anything, quite low. Which is typical with Blackstone.

 

[AITG]

I also had high fuel dilution on a new engine (search F53 in this forum). The dealer checked fuel trim for an injector over-fueling and found nothing out of spec. I have made a point of getting the engine fully warmed up before draining and changing my use of the transmission tow/haul mode. I'll continue to watch it but wear metals are dropping nicely.
I agree with trying a different lab: I use Polaris in Indianapolis.

 

[rubberchicken]

I had a UOA that showed high fuel dilution on a motorcycle, about 5%, and the wear metals were higher than normal. After much digging I finally found a bad spark plug resistor cap. Fixed it, and next UOA was right back to normal- normal wear metals, no fuel dilution.