[Manxman]

I have been changing oil at 6 month intervals, regardless of mileage, as my daily commute is only 10 miles each way and in winter the oil barely reaches minimum operating temperature (160F). Oil changes done by dealer.
I have been sending a sample to Blackstone at each change and for the first time the % of fuel in the oil was way over spec at 3% - previously it was 0.5% and 0.8%. The car has had a few good long runs recently, but very little aggressive driving, given the road conditions and primarily suburban driving. Only 5,000 miles in the past 6 months and 15,000 pn the motor.
Any ideas if this represents a problem? A function of recent frigid temps perhaps, or a sign that the car needs some "exercise" when the weather improves?

[sy2767]

My car suffers from the same commute and very frigid temps, i checked under my oil cap today and it was no surprise to see a little white residue from the car not reaching full temp and burning off the condensation that builds up from temp cycling etc.. The car runs richer when its cold (hence the higher fuel % in your oil) and it never gets hot enough with short trips and cold weather to evaporate which is a normal process in the summer months, all i can suggest is more frequent oil changes in the winter to keep the percentage lower and drive the car more often and let it get to full operating temp for awhile.

[parabola]

Just drive the damn thing.

[tc535i]

Does the car run richer as it gets colder, or when it's "cold" it runs a certain way?

That is to say, if a car is driven for 2 minutes in a 60f temp or a 20f temp, would it run the same air/fuel ratio in both since it's "cold" (water not up to temp) , or would it run richer in the 20f scenario?

[sy2767]

Originally Posted by tc535i

Does the car run richer as it gets colder, or when it's "cold" it runs a certain way?

That is to say, if a car is driven for 2 minutes in a 60f temp or a 20f temp, would it run the same air/fuel ratio in both since it's "cold" (water not up to temp) , or would it run richer in the 20f scenario?

Based on my own observation and knowledge (take that for whats it worth..lol) the colder the ambient temp the richer the fuel mixture is until the car warms up, ( the car measures air intake temp to measure this) so if its -30 as opposed to -10 it will take longer for the car to reach operating temp based on the colder temp

[runningdoc]

In general, cars run richer as the temperature drops. This is one of many reasons one sees gas mileage that tends to fall off as the temperature drops. Other reasons mileage drops include increased oil thickness, and an increase effect of friction in general (think about shifting a manual transmission at 85F vs. shifting that same transmission at -10F) and a greater overall wastage of energy - tires spinning on snow/ice in starting, etc. Essentially, it is analogous to the old days with an engine with a choke device, allowing the engine to run richer when cold, and then as it warms, the choke closed manually (i.e. the driver would close the choke line), leaning then engine out as the older engine would not run too rich (would stall, flood, etc). The only difference, is now it is all programmed into a chip. Does this help?

In general, in winter (and even in spring and summer), the old adage to drive a car long enough for it to truly warm up holds true. The moisture evaporates from the oil, and the exhaust system among other places...

[shata]

During very low temps sometimes it helps covering radiator half with piece of cardboard. And monitor temps from there it may keep engine little warmer like it should be. Coolant system is very good unfornately lol

[Bob Shiftright]

Did the "comments" section of the Blackstone report say anything about it?

My guess was it might be due to the short trips with a DI motor, but I looked at a couple of other 335i reports posted here http://www.bobistheoilguy.com/forums/ubbthreads.php and high fuel in oil doesn't seem to be a typical 335i finding.

[benjlv]

you should try to take the long way home once a week or so. it should help boil off all the water and fuel out of the oil.

[Manxman]

Originally Posted by Bob Shiftright

Did the "comments" section of the Blackstone report say anything about it?

My guess was it might be due to the short trips with a DI motor, but I looked at a couple of other 335i reports posted here http://www.bobistheoilguy.com/forums/ubbthreads.php and high fuel in oil doesn't seem to be a typical 335i finding.

They referenced the frequent short trips and cold temps. It was the big increase from this time last year that surprised me - 0.8 to 3.0%. Given the road conditions the turbos have been working at low boost, so I'm guessing any ring blow-by is due to cold starts?

[sy2767]

Originally Posted by Manxman

They referenced the frequent short trips and cold temps. It was the big increase from this time last year that surprised me - 0.8 to 3.0%. Given the road conditions the turbos have been working at low boost, so I'm guessing any ring blow-by is due to cold starts?

Has nothing to do with low boost, it's the car dumping fuel in the cylinders while they are cold and the rings, pistons not fully expanded yet because the metal is still cold, hence some fuel gets past the rings into the oil, so you are correct guessing its ring blow by.

[DrSeuss99]

you mentioned that the oil change is done at the dealer so i assume they took the sample for you? did they do it while the engine was still hot and get the sample mid stream?

not sure how much this would affect your results but it is recommended...

[DF]

I change my oil every 7,000 miles. It is brown.

[rowingone]

Given todays computer controlled cars . . that compensate for changes in air/fuel about 4 times a second . . I dont believe that cold temperatures would have that dramatic of an effect . . I agree with the previous poster about where the sample was taken as being the biggest factor. If they took the sample from the top layer of the used oil . . and gas is lighter than oil . .

[techwhiz]

Originally Posted by parabola

Just drive the damn thing.

+1.

In the last two years my car has been 45K miles.
My daily commute is ~43 miles each way.
Operating temperature? My car makes operating temp on just about each start.