Here is the deal. I changed the oil in my car in April 2007. I am using Royal Purple oil with a Wix filter. I have put 650 miles on the car since the oil change and actually replaced 2 quarts (don't ask how I lost the oil).
When should I oil change again? I was thinking of not worrying about it until Spring 2009.

 

synthetics should be good for 5k miles or 6 months to a year-whichever comes first. You can tell a lot about the oil condition by checking the color on the dip stick.

 

Sorry to be blunt, but this is absolutely, positively, NOT true!! You can tell very little about the oil by looking at the color.

 

I have never seen a engine that didn't contaminate the oil and change the color and feel. I also totally disagree with the recommendation of some of the manufactures. I know a guy with a Porsche SUV. They recommend changing the mobil 1 every 20k miles. Oil is cheap compared to repairs IMO.

 

It's suppose to change!!! That's what the oil does. It holds dirt and contaminants in suspension so they don't get on your bearings!!
I'm sure the manufacture, the SAE, and the petroleum industry could benefit from your knowlege. Perhaps you should publish a paper with all your data from all the test and research you've done over the years. Petroleum chemist and engineers make big money doing this.
The assertion that I'm going to suffer oil related engine failures if I don't change my oil sooner than the manufacture recommends is nonsense at best. Porsche would NEVER risk the warrenty claims or law suits that would occur if the oil wasn't good for well over the recommended change intervals.

 

Thanks for supporting my view on visible oil contamination. There are a number of factors that play into the rate of contamination. Heat and cool cycles, engine condition, evac system efficiency, type of driving, etc. I suppose it is ironic that Exxonmobil does not recommend these long change cycles? If you are comfortable running contaminated oil and filter for long periods, do so. oh, and my complements on doing such a nice job of highlighting my quotes.

 

I did my last change on the Z at ~6k, very reasonable with a synth in a modern engine. But I'll add this caveat: if it's on your carb'd 86, recommend you stick with 3k changes, especially if you do a lot of cold starts.

Reason: carbs don't have anywhere near the fuel control of injection. Every time you hit the throttle, the accelerator pump shoots raw fuel down the throats. Not all of this fuel is vaporized, a percentage gets into the cylinders as raw fuel, some of that contaminates the oil. Same thing when you are running with the choke on, cold. If no choke, I know you have to pump the pedal a few times to get it to start/warm up.

Also, do you fully warm the car up and run it at temp for enough time to help burn off moisture that naturally accumulates as a byproduct of the combustion process? Whenever I fire up the 71, I make sure it comes all the way up to temp and run it for a while, throwing in a couple of WOT blasts for good measure.

I've seen internal components from limited use engines that were surface etched by the acids that moisture in the oil helped form. Yet the owner thought the engine must be in good shape cause they only fired up their classic once in a while for a short time. That is actually very tough on engines, and would call for even shorter oil change intervals.

On the oil selection itself: do you have a flat tappet or roller cam? If flat tappet, you might want to pick an oil with zinc in it, or add zinc as a precaution. Newer spec oils have had the zinc content reduced to protect emissions equipment. I add a bottle of CD-2 Street Legal Oil Boost to the synth I run in the 71 to protect the cam; the stuff is loaded with ZDDP. I'm not familiar with RP or it's zinc content, but I have read some negative stuff about it, e.g.:

http://forums.corvetteforum.com/show...light=failures
http://web.camaross.com/forums/showt...ighlight=royal

Also recommend you use the longer "truck" filter if it fits in your app. More filter area, same price.

 

Id have to agree after X amout of miles all oil looks dirty.

On the next note, sure synthetic oil can last 15k miles, I believe the main reason for changing oil every 3k miles is because the dirt that gets built up. Kinda like say you can use the same dish water 500 times and expect the same results as clean dish water.

 

My biggest concern would be moisture. When I first got my '96 it was driven very little because I had a company car. I still changed the oil somewhere between 4-6 months. Maybe that was overkill - it was nowhere even close to 3,000 miles in that timeframe - it just seemed like cheap insurance to make sure there was not moisture built up.

I just bought a 2000 that the owner claimed was not run significantly for at least a couple of years. I don't know when the oil was changed last honestly. But when I pulled the oil fill cap the underside looked like it was raining in the valve cover.

 

From the Mobil page.
http://www.mobiloil.com/USA-English/...rformance.aspx

It's ironic all right. They're even recommending 5000m on their non-synthetic oil.

 

Quote:
You've never seen an oil like this before. Mobil 1® Extended Performance is a high-endurance motor oil designed for longer service intervals. It is a fully synthetic formulation that helps extend engine life, reduce oil breakdown and minimize engine wear -- all while helping to keep your engine clean. Improvements that add up to exceptional protection for 15,000 miles. Guaranteed.

Yep, already read that. Extended performance Mobil 1 is the specific oil. Not regular old Mobil 1, and only to 15k.
Your reply is weak at best. Like I told you earlier. If you want to run your oil that long, go for it. You are wasting your time and bandwidth as far as I am concerned.

 

The cam is part of the Edelbrock Performer Package. I didn't do the build, I'm not sure if it is roller or flat tappet. It is a new (~2000) crate engine rebuilt, guessing it is a roller cam.
It is choked, however she does need to be pumped to get her to start. I tend to drive her like I stole her. She was actually getting a little too hot, never boiled coolant, just sitting high on the inaccurate gauge in the car. Replaced the radiator and temps are a lot cooler.
I figure I'll change the oil every Spring, I only put 630 miles on her last year and plan on about 1500 this year since the hot running problem is solved and I am slowly learning to tune the carb.

 

With that low miles and possibly running rich, who know what's in the oil? I wouldn't leave it in there for 2 years, no matter what kind of oil it is. "angel71rs" covered it all. Hard to believe anyone would put a flat-tappet setup in a car these days, though.

 

Most Performer cams out there are the mild flat tappet hydrualic cam version, 204, 214 @ .050 IIRC. I've installed the Summit ripoff on a couple of engines; guys weren't interested in big HP, just wanted something that would give decent torque/mileage. There are roller versions tho, so only way to tell for sure is to look. And there are Performer RPM versions of each, much more lift/duration. If engine has a smooth idle, it's the Performer, if it's a little rough, probably the RPM.


Won't hurt anything to add an additive with zddp as a precaution with any version.

 

I sent a e-mail to Exxon/Mobil about frequency of oil changes. I told them I drove my F-body car 2500 miles a year, and wondered how many years I could go on their 15,000 extended service Mobil 1? If nothing else, it had to be a laugh maker for them last Friday. Here is their response.

You will need to change the motor oil once a year regardless of mileage
accumulated.

--
Thank you for choosing ExxonMobil products.
If you need further assistance, please contact ExxonMobil at 1-800-ASK-MOBIL

-Matt Jacob