Oil Change....

[NCGuy68]

The conventional wisdom is to change oil every six months no matter how many miles are accumulated. What about show/storage cars that may only see minimal miles during a six month period?

What degradation could occur to the motor during this time frame?

[NCGuy68]

Surely someone has knowledge on this subject.

Is synthetic or fossil base oil best for low useage and/or slightly driven show cars?

[Kurt S]

I don't subscribe to this theory (and I used to work in the oil industry).
Mileage matters, time doesn't. High mileage is obvious. Low mileage is bad if the engine isn't brought up to operating temperature so that some of the 'undesireables' (that got in the oil during start up) can gas/flash off.
Worst case is the people who start the car once a month during the winter and let it run for just a couple of minutes.

JMHO, I know others will have other opinions.

[YENKO DEUCE REGISTRY]

I agree with Kurt, just some hype to make you buy more oil. I also disagree with changing the oil every 3k miles in your everyday car - unless you are going offroading or towing some horses. I got 192k miles out of a '91 Grand Prix SSE and changed the oil every 5-6k miles. So, I believe the 3k mile oil changes are also a ploy to make you buy more oil!

I'm not completely sold on the synthetics yet, especially to break in a newly rebuilt engine. I know GM uses it to break in all of the LS1's etc... but,

[jg95z28]

If you're not going to change the oil as frequently, then I'd say go with a synthetic. But that's just my opinion.

[Kurt S]

I do shoot for 5K between changes. I consider it cheap insurance.
The basic issue has changed over the years. The VI (viscosity index) improvers that are added to the oil to make is thicker at higher temps (giving it the multi viscosity rating, eg 10W-30) used to break down. Now they've extended the life of these and other additives. Hence the longer recommended oil changes.

I don't run synthetics in the daily drivers, mainly due to cost. But have in the past, esp in manual trans'.
I will be running it in the Z, esp the trans and axle. I saw where there was a Hemi that couldn't break the 11's. Changed to all syns, that did it.

[Jeff H]

I used Mobil 1 synthetic in my old supercharged 93 Z28 Indy 500 Pace Car. Car ran great with 74K miles on it and a little over 40K with the supercharger. Right now I run Castrol Syntec in my SS454 pickup and it's the cleanest looking oil I've ever seen in an engine after 5K miles. But then my engine is also only 7.9 to 1 compression so that may contribute to it looking so good. If your car has ever sat through hot, cold, and humid conditions in the garage, then I would bet there's some moisture buildup inside the engine. If you don't get a chance to run the engine for a good 20-30 minute drive every other month then I would change it after 6 months or longer if it has been sitting. It's cheap insurance against a rebuild.

[NCGuy68]

From the oil analysis I've seen, full synthetics have no advantage over fossil oil in slightly driven show/storage cars.

On the other hand, I do agree that once fired, a car should be driven until it is thoroughly warmed up.

Any other thoughts on this subject?

[budnate]

Well on the flip side, I have always been more concerned about old gas causing problems in the carb and valve springs laying fully compressed for months at a time, so I fall under the guy that will run it for a few minutes to circulate stuff around and shut here down only because it is backed in the garage if it was aimed the other way I would probably let it warm up, if the oil and filter is good quality it will do its job. and most ex-systems can handle moisture just fine these days.

Bud.

[Kurt S]

Bud,
I've put up a car over the winter every year (standard practice in MI). Never had any issue other than battery drain on some new cars.
Carb will be fine for six months straight, maybe longer. Valve springs better be a non issue if they were designed and built right. If you're going to store for 5 years and had a big cam, then I'd back off the valves.
Running it that little is *really* hard on the exhaust.