heck i think oil can sit forever.

 

Depending on climates, I agree. Filters go by mileage period. Good oil that don't see extreme climate changes are fine for two years with low mileage.

 

So can i infer that diesel fuel does not contaminate the engine oil in the same way as gasoline does on cold starts in gasoline engines?

 

Lex2002, there certainly can be diesel slippage past the rings, but that is generally only a real issue if either your rings are worn pretty bad, you're runnign excessively long idle times with minimal "run time" between idles, or you're running something as new or newer than the '08 Fords (their active regen cycle on the DPF system can easily provide excess fuel contamination into the oil sump).

Generally speaking, if you're not running excessively long and frequent idle times, your oil system gets hot enough to where any minor fuel dilution gets volatilized while running down the road.

 

Ok, so let me be more direct:

What's the longest period of time you would run the same engine oil before reaching 8000 miles driven?

 

What do YOU think will deplete in your oil during the time it's not running?

Lotsa' stuff happens to it when it's running.

Just sitting there? Not so much....

Do you need a numerical answer? How about 30 months?

Pop

 

Since I've never been in that situation with any vehicle I've ever owned, I would probably be asking for some opinions like you are, but I honestly don;t have an answer to that question.

Thinking off the top of my head, I would probably let it stay in the vehicle for as much as 3-5 years and then change it just for the heck of it. If really pressed, I would choose 3 years just to be on the conservative side.

Keep in mind that most engine oil manufacturers will say that the shelf life of an unopened bottle of engine oil is 2-5 years, and that is because if the oil goes through repeated warm/cold cycles, some of the additives can separate. Since you're running your truck periodically, though, it is not getting enough time for any significant separation, any separation which MIGHT take place should be completely resolved and re-mixed every time you use the truck.

 

My oil currently has maybe 4000 miles on it and 1.5 years. Im gonna send a sample to Blackstone and see what they recommend.

Would be a shame to toss $100 for oil thats only half way through its life.

a

 

Let us know if they report anything out of the ordinary due to sitting. I too, seldom use my PSD more than a few times a month.

 

I'm running an '02 F250 4x4 Super Cab with 172,500 miles on it now, which is my first diesel, I ran the first oil change out to 6,000 miles in 16 months with no usage, on the present OCI I've gone 4,500 miles in 4 months due to a trip. I'm going to try for 7,000 miles before changing unless the oil level goes down. I guess what I'm saying is that I go just by mileage since all my driving is highway and very little towing. If you're comfortable with 8,000 miles with the way you use your truck then just run it til you get there. I may try 8,000 miles my next go around if I make it to 7,000 miles without any usage this time. As far as time with your 8,000 miles, I think 2 - 2 1/2 years is reasonable, with no more than two winters though...just my opinion.

Last year I dumped my filter after 3,500 miles and topped off with 2.5 quarts of MMO for the "winter" months to lower the viscosity and help maintain a clean engine and I left that in until July of this year with no usage in the final 2,500 miles. I'm debating on whether to do that again or just see how the Delvac 15w40 does on it's on here in North Mississippi...if it starts getting down to 20 degrees faster than it did this past winter I'll probably do it as I had no problems starting at 20 degrees last winter and never used the block heater.