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Series 60 Fuel dilution.

1999 series 60 with 1.1million original miles. Just bought it. The old owner was running 15W40 full synthetic oil. He had very good maintenance records and showed me that the oil only had 15k miles on it and said he had been changing the oil every 30k. I bought the truck ran it for 15k miles more and at 30k changed the oil and sampled it. The oil sample came back 3.5 fuel dilution from Polaris labs. What should I do. I've never had an engine with fuel dilution before. Thanks.

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Rick I am not sure what you've done so far but I would check fuel injectors.

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Thanks Mel, A good Detroit shop, they should know how to troubleshoot this? Right. This is the same truck that you recommended we replaced the throttle position sensor on. You were absolutely right, that fixed all the problems I was having. When we checked the codes at that time it gave a code for the tps and #2 injector. Since it ran so good after replacing the tps I didn't look farther into the injectors. But now I noticed a slight irregular rough idle sometimes almost like one cylinder isn't running right. I have a good Detroit shop hopefully they can troubleshoot this. At 1.1 million if they find a bad injector would you just change all 6 of them. Thanks again for the help

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Don't be chasing problems that may not exist. Reading oil samples is looking for trends. A slightly rough irregular idle on an old Detroit is normal. you may buy injectors that are worse than yours, and you are very close to overhaul time. Keep driving and sampling, look for wear metals trending up. Putting some injector cleaner in your fuel several times a monthis a good practice. That fuel dilution in a first sample is to low to warrant action.

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Rick I found this on Polaris labs website. ( Fuel Dilution is the amount of raw, unburned fuel that ends up in the crankcase. It lowers viscosity creating friction-related wear almost immediately. Dilution levels above 10% could cause a crankcase explosion

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On a old Detroit, its probably coming through with the blow-by. Blackstone labs may still be using flash point to measure fuel dilution. The gas chromatography may be picking up partly burned fuel in the soot. Split a sample with them next time.

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Rick will be eternally grateful.
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