Changing Oil...

[2ndBimmer]

Ive had my 318ti for about 2 months now (RIP my 320i) and have shoved about 4000 miles on the odometer (part of this driving to SC to the BMW driving school) and figure I ought to be changing the oil soon.
I still have some quarts of 10-40 (for winter) and 20-50 (for summer) leftover from the old car; whom drank the stuff on a weekly basis.

What weights do you recommend? Classic petrol or synthetic?

The car has close to 100k on it now and the engine is often run to 5000+ while accelerating.

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Green 97'

[DougZ]

I personally use full synthetic 5W-30, just because that is what BMW recommends for my car and what was in the car when I got it from the dealer. Comes out clean everytime, so I like it.

[J!m]

I would go with the same weights you used on the 320, in the same seasons. I assume by that you drive it year-round.

I run 20-50, but only drive in the summer. (Mobil has a nice 15-50 now)

If you go full synthetic, let it ride the full dash-light ride, changing the filter about 1/2 way through the green lights.

If you go Dino-oil, dump it and change the filter 1/2 way through.

The cost will be about the same either way. Don't forget to check your oil level at every fill-up. It may not plow through it like the 320 (or my old '71 Land-Rover), but it WILL USE OIL! I easily burn up a quart or so every 7-10k. It's been that way since new. The lighter weight oils will go through the motor faster (my experience).

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"Speed's just a question of money. How fast you 'wanna go?"

[2ndBimmer]

Thanks for the advice. Im still curious as to the preformance/longevity difference between classic and synthetic, but since I have 17 quarts of Castrol 20-50 leftover Ill be using that.

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Green 97'

[Travis]

2nd Bimmer:

Dino Oil has some crud in it that is left over from the dinos.
Synthetic is just that, so the leftover crud (generally described as "waxes" (whatever) just aren't there. The synthetics that aren't are especially purified dino oils and sit in the middle of the price range.
Two or three bad things can happen when you don't change your oil often enough.
1. Your oil gets hot, crud congeals and falls out of the oil. This contributes to general grossness in the oil pan, and the least harmful thing that happens is that it builds up over time and infrequent oil changes. This effectively reduces your car's oil volume which means that your oil is hotter, the pan's heat-sink capability goes away, and effective oil volume is reduced (It's kind of a circle).
2. Your oil becomes acidic from blown-by combustion products. The older your oil gets, the worse it gets.
3. Your oil gets full of crud, breaks down, and it's crud-carrying capability degrades.
All of this yuckiness means that lots of people change their oil too much. You really are ok if you change your oil when the light turns yellow. The brightest lube engineer I know also runs a grain farm in Central IL. the guy uses Mobil 1 in his tractors, and changes it EVERY OTHER time the manufacturer recommends (the filters get changed every time).

[Travis]

2nd Bimmer:

I should mention that the engine is a personal test project (obsession), which is why he's being kind of mean to it. Also, after 3000 hours (That's 150,000 miles at 50mph) the tolerances for the internal engine parts were within manufacturing tolerances.

I personally use a semi-synthetic and change the oil the same week (usually) that the light turns. I don't worry a bit, but discussing oil changes with car people is like religion, politics, etc with ordinary folks.

Travis