First service: 15k miles or 1 year ?

[JCL]

Originally Posted by martz

Ok fine if you choose to do it at 7500 thats sure is better than 15K. I do not believe I am wasting my money at 3k intervals.... to each his own ....below is a post I pulled from carbibles...

So how often should I change my oil?

You can never change your engine oil too frequently. The more you do it, the longer the engine will last. The whole debate about exactly when you change your oil is somewhat of a grey area. Manufacturers tell you every 10,000 miles or so. Your mate with a classic car tells you every 3,000 miles. Ole' Bob with the bad breath who drives a truck tells you he's never once changed the oil in his car. Fact is, large quantities of water are produced by the normal combustion process and, depending on engine wear, some of it gets into the crank case. If you have a good crank case breathing system it gets removed from there PDQ, but even so, in cold weather a lot of condensation will take place. This is bad enough in itself, since water is not noted for its lubrication qualities in an engine, but even worse, that water dissolves any nitrates formed during the combustion process. If my memory of chemistry serves me right, that leaves you with a mixture of Nitric (HNO3) and Nitrous (HNO2) acid circulating round your engine! So not only do you suffer a high rate of wear at start-up and when the engine is cold, you suffer a high rate of subsequent corrosion during normal running or even when stationary.
The point I'm trying to make is that the optimum time for changing oil ought to be related to a number of factors, of which distance travelled is probably one of the least important in most cases. Here is my selection in rough order of importance:

1. Number of cold starts (more condensation in a cold engine)
2. Ambient temperature (how long before warm enough to stop serious condensation)
3. Effectiveness of crank case scavenging (more of that anon)
4. State of wear of the engine (piston blow-by multiplies the problem)
5. Accuracy of carburation during warm-up period (extra gook produced)
6. Distance travelled (well, lets get that one out of the way)

I really doubt that anything any of us say is going to change your mind about how often to change your oil. However, here are a few things to think about, perhaps others may find it interesting:

• 3000 mile oil changes were common when large amounts of byproducts of the combustion process contaminated the oil. There are still byproducts being produced in engines, but the factor by which they have been reduced in the past few decades is exponential. There is a reason they are called LEVs and ULEVs. Less out the tailpipe, and less into the oil.
• Those older vehicles had 4 quart sumps most of the time. Your 8 quart sump can hold twice as many contaminants in suspension, while having oil that is exactly the same in terms of being clean or dirty. That change alone would support doubling the oil change interval. On large stationary heavy duty engines, doubling the sump capacity is standard practice to double the oil change intervals. It is simple math.
• Your car bible article is dated by the reference to carburetors. It must be the Old Testament. It is over thirty years out of date. Oil has changed in that time.
• Oil is a non-renewable resource. How can you consume so much and not consider your impact on planet earth? 3000 is five times as often as 15,000. Five times the recommended consumption, when translated to fuel consumption, would be the equivalent of driving a vehicle that gets 3 mpg. Does that seem normal?

Anyway, as you said, to each their own. For my part, I think that modern engines and lubricants are hugely different than those from the sixties and early seventies. I understand old school. I changed my oil at 3000 mile intervals back then as well. Now I go 10,000 miles, sometimes 12,000. I hit the time interval before the mileage interval.

Good luck in whatever you decide to do.