I used 5k to 7.5k as a good number depending on your driving habits, the environment you drive in as well as the type of gas that you have available to you. All things being equal. You probable could go 10 to 12K with no problem but why push if you dont have to. This isnt the first car that I've own that used synthetic oil, (Mainly Mobile-1). In every situation at around 7.5K miles, I notice that the oil had alot of junk in it, carbon, particulents. The color was very dark and the filter was finished. I also notice after a oil cahnge, My gas mile went back up and the car ran better. I dont always drive hard but city traffic jams in the middle of a 100 degree summer with the air on is a killer on engines. In the end, its going to be up to you and how well you trust your oil.

 

A couple more points - Regarding oil in my engines, I don't trust:

1. Instincts
2. Feel
3. Color
4. looks
5. Tradition

I do trust an oil analysis. Oil does three things - it cools, it lubricates, it cleans. It will always cool as long as the volume is there and it remains a liquid, it will always lubricate. The cleaning part is what wears out. The last oil analysis I had done Blackstone labs said I could have gone another 5K miles and the sample was over 12K. I've attached a couple of pics of my engine with cam covers off, now at 75K miles and I've maintained this engine since 10K with only 12K change intervals, 2 interim filter only changes at every 4K, and synthetic oil.

Just like changing tires every 5K miles would be a waste of money and good product, dumping synthetic oil as soon as 5K 7.5K, even 10K is a waste of good product that was specifically designed to last longer.

 

Realized I had a pic of my 97 BMW 2.8L w/cam cover off. This engine has 104K miles on it - Most of its life it's had 12K synthetic oil changes with 2 filter only changes at every 4K. I do drive this car considerably more aggressively than my Jags, which are mostly city cruisers, grocery getters.

 

them there is pretty clean, not a hint of sludgy material anywhere, but...can you identify the tree that this leaf is from?!!?



Sorry OP for the off-topic question.

 

nice running gear !

 

Of course! - Acer Rubrum....At times like these, it pays to be a T.E.C.H.

 

I would have said 'southern maple' 'caus I don't speak Latin.

tp

 

That leaf needs to be changed its not even green anymore.

 

Gold Star Steve! Best T.E.C.H. we got. lol

Now, back OT, since I've been reading all of the posts in the last few years about synthetic vs dino oil, I've been letting my changes go longer than the 4k, was 5k, now I'm going to 6k w/o any filter changes mind you. I think that'll be my limit though.

 

Well, I almost "converted" you. At least I got a little more mileage out, but then again, you Texas boys don't need to conserve, you have ALL the oil you can use....and then some.

I wish I could affort to pay the $20 for everyone's first oil analysis, because after you saw the results....Aw, never mind. I bet even with the results some would still say - "My dad always changed the oil in his 57 Buick Roadmaster every 3K miles and if it was good enough for dad....."

 

Yup- or a hundred other non-scientific methods to justify it. I liked your response above regarding how NOT to make a decision but fear that you're

Mike

 

I did pay for an oil analysis at 10k miles (106k on the car) and the report was that the oil was just fine, good for at least another 5k miles before a retest.

 

Well now, Test Point, the relevant info would be what brand and viscosity of oil, and which oil filter you were using.

As for me, I bought my Jag used. It is a 2001, and had 29,000 when I bought it. It was practically immaculate, so I felt like the previous owner took pretty good care of it, but I changed the oil right after I bought it, and decided to shorten the mileage between changes for a while to hopefully "clean the engine out" if it was not very clean when I bought it. I am no automotive engineer, but my own instincts, over the years have seemed to teach me that you can get some feel for how dirty the inside of an engine is by changing the oil and then driving it for a week or so and then looking at the color. If it still looks pretty much the same, and has that honey look, I have to hope that there is not a lot of sludge in it. If, on the other hand, it is already turning brown, I have to think that either there is some sludge in there, or there is something about how the engine is running that is not so good. The first car I ever bought was a '68 Cuda in 1972 for $600. It had about 48,000 miles on it. It ran pretty well when I test drove it, and ran OK for a few weeks. Then, things started to come apart. It seems that the guy had put sawdust in the auto trans, and the engine was so gummed up that the valves did not open and close properly, and the rings on the pistons did not hold the compression well enough. Our local mechanic told me that I could try to "clean out the engine by taking the oil out, replacing it with kerosene, then starting it and letting it idle for about 20 minutes or so, and NOT to rev it up!!!" OK, so, I did that. The end. That was the end of the engine. Got an "engine swap" from a shop and a new trans and it ran like a bat out of Hell (318) but with an annoying tick from the lifters. Kept it about another year and then sold it and bought a 340 Duster, and that is another story entirely.

Sorry for the long post, but that is my oil story. Since then, I tend to keep my oil changes in the moderate to lower end of mileage. I do about 10,000-12,000 on my Dodge van (synthetic) and I am going to do about 5-6000 on my Jag (that is a year of driving)

In the end, if you recycle your oil you are not hurting the environment, and I'd rather change it too often, than not often enough.

 

As stevetech pointed out above, these methods are not reliable in the least and pretty much as accurate as reading tea leaves. If it were that simple and consistant, we would do changes comparing oil colour on a colourimeter. Jaguar would have a built in one no doubt.

Formation of sludge, the harm it does and whether to remove it or leave it alone all compared to engine life is a whole science of it's own.

 

I believe that long-haul trucking companies have moved to oil analysis rather than miles for changing many times the volume of oil in our cars. The objective is to maximize the economic cost of a change verses wear on the engine.

Oil has changed dramatically in the past 20 years.

 

I don't want to sound mean but if you change your oil at 10k on a gas engine you are stupid...go to my profile and look at the engine pics I have.that is from 10k oil changes...I'll finish and post all that like I was goingto A long timd ago

 

"I don't want to sound mean but if you change your oil at 10k on a gas engine you are stupid.."

I've said my piece, I think 5K is reasonable. That being said, EVERYONE is entitled to his/her opinion. Let's keep it civil.................
Brian

 

OK, I looked at your pics. Looks like a bunch of dropped valves, probably from a slipped or snapped drive chain. What's that got to do with oil?

 

Hey, we all agree that it personal preference one when to change your oil, whether synthetic or dino, lab tests can be helpful, some like to play it more conservative (like myself), why is it that all these oil change threads end this way.

Gonna close this one, its served its purpose.