aircooledpurist

My oil was changed by the previous owner just under 500 miles ago in May of 2018. Should I change the oil immediately, or drive it this summer and change it in the fall before it goes away for the winter? I guess my question is do I worry about miles, or change it out once or twice a year regardless of how much it is driven?

rk-d

You’re going to get a lot of opinions.

In my opinion - if it’s been a year, change it.

Railmaster.

Twice a year after limited miles? Once a year is more than ok if you drive 5000 miles a year! And if you drive 2500 miles a year you can probably change it every second year!

Miles or time or both are the questions!

Edit: 500 miles? If the engine is fullt warmed up every time you drive then you can wait another year!

Todays oils are long lasting, when your engine finally needs a rebuild it's not because you changed the oil every second year if you drove less than 2500 miles a year!

AOW162435

I change mine annually, regardless of mileage. In the nearly 14 years I’ve owned the car, I’ve rarely exceeded 3,000 miles per year.



Andreas

tstafford

I'd do it annually or at 6K miles whichever comes first. But my bet is that is conservative and that it could go much longer. But it makes me feel good.

pp000830

Has anyone had one of those dreaded oil related engine failures that are graphically shown as violent events in those oil advertisements as the result of not changing their oil often enough on their 993?

HelpMeHelpU

Funny, I asked this question of myself just this morning. Bought my (36k) car last August and changed all fluids immediately. By the time of its first anniversary with me, I'll be surprised if I will have put 3k on it. Changing it after so few miles seems wasteful but I'll probably do it to preserve the car's great pedigree.

ed devinney

Opinions vary, as do conditions, but here's some data.

I've used mobil 1 in my 993 and 951 forever, and usually have it analyzed at Blackstone when changed. The 993 is street driven only, and not terribly hard (I recently pulled the engine and clutch still had plenty of meat at 50k miles). Per the analysis I could go 10k between changes but stick with 7500 miles. I've let the 993 go 2 years between changes with no appreciable gain in water or change in pH. The 951 recently came out of about 4 years of hibernation. I changed the oil before starting it up, but per Blackstone that really wasn't necessary.

tl;dr: the one-year rule won't hurt, but probably isn't required.

bw993

The two things that are the enemy of engine oils of all kinds, other than material contamination, is the carbon cracking of the oil and moisture build-up (H2O) that changes the pH of the oil. Carbon cracking is a process where the carbon oxygen bonds are broken at the molecular level and the free oxygen atom bonds with hydrogen to form an OH pair. This combination usually results in an acid build up in the oil (i.e. acetate acid). The burnt/sour smell in used oil is typically from this build-up of acid. Carbon cracking of the oil occurs due to high oil temperatures (obviously), but also during high strain/shear stressing of the oil and during periods of oil cavitation. Moisture build-up in the oil occurs when you have naturally occurring condensation in the oil sump due to the differences in engine temperature and air temperature, when you engine is not running. Your oil is contaminated by this surface condensation during the process of starting your engine. This condensation build-up is worst for a car that has frequent short trips and multiple starts in humid environments. Of these two, carbon cracking is the worst since the acid build-up occurs rapidly, will cause the oil to clump with no lubrication properties and will pit/varnish your internal engine parts.

In theory, oil that is just sitting in a clean oil sump should stay in good shape indefinitely. If you use a car rarely, when you go for a drive make it a long one.

IMHO

HelpMeHelpU

Thanks so much for this explanation. When you say, "Make it a long one," about how long should it be (ideally)....or, perhaps, not shorter than X time?

aircooledpurist

Thanks to everyone for some very good information. Happy Memorial Day!

TheOtherEric

+1. IMHO, if you drive 5,000 miles per year, change it every year is common practice. If you drive 500 miles/yr, every 2-3 yrs is fine.

Railmaster.

This!

pp000830

Interesting that in the absence of clear cut facts opinion reigns supreme.

ed devinney

Yes, that would be why I made my decision based on years of lab analysis