Synthetic Oil Changes

Depends on the kind of driving you do. Changing the filter only removes particulates, not acids, and other crap from condensation in the oil sump.

If you're on the highway all the time OK. For driving around town, dump the dino oil every 90 days and slap a new filter on at the same time, regardless of mileage.

Lg

thanks!!

any other tips?

Tips depend on skill level of car owner/operator ;-\

One that is a Safe Bet: clean your headlights, turn signals, stop lights when you fill up at the gas station, using their window cleaner and sponge.

Lg

Just Googled "compare oil filter specs" and found some interesting stuff. with GM's OLS expectations are 4,000 mi. to 7,000 mi. With highway driving you could do as much as 12,000 miles. GM senior project engineer Robert Stockwell has been studying analyzed oil samples from vehicles with OLS. This GM spokesperson has revealed tests where done w/ regular petroleum based oil, that showed oil change intervals of 10,000 mi. ,

14,000 m. and even one did 16,000 miles. With synthetic lube and superior filters you could do even more. For curiosity, an occaisional oil analysis might be interesting.

No doubt that the additives work in the way you describe: A matrix or film develops on the surfaces. I have suspected that the introduction of air at the oil change time may be involved in the effect. Iron concentration seems to go up right after a change, which would be consistent with increased wear OR scavenging of the oxygen which was introduced. Just a hunch.

My car manual divides driving into *severe* and *other* Severe being a lot of short trips, stop and go, city driving, driving in dirty/dusty environments, pulling a trailer, etc etc.

Under *severe,* more frequent oil changes are recommended, and the number drops from your 9 billion miles down to 3,000 miles.

Some of us haven't forgotten how to read.

Lg

"Your 9 billion"? I don't understand your smart-assed post. For someone who claims to be able to read, 9000 is not 9 billion. And there's really no reading to it in my case. My oil light comes on sometime after I've driven

9,000 miles s>

They:

1) Misread 2) It's a joke.

Don't take everything so seriously and rant on it.

And please don't top-post - fix your borked OE.

Laurence has a habit of believing what is written in his owners manual and sometimes thinks that it also pertains to other people's cars. The idea that new oils, new engine designs, and new computer technology might allow people to do other than follow the old wives tale of "change the oil every

90 days/3000 miles" is tough for some people to grasp.

And I hate bottom posters - particularly ones (not you, to be sure) that post a non-comment at the bottom of some extremely long thread and don't have the courtesy to clip the thread. If I see a top post and I'm curious about the rest of the thread, I can scroll down. Usually, I'm reading the thread consecutively so I already know what's down there. Top posting is the best way for me...

Brian

This is true. However, unless you are actually doing an oil analysis (and a lot of truck places and fleet maintenance places will do an oil analysis for you, and it's not expensive), you don't really ever know about the condition of your oil.

Modern oils do some things very well, and the synthetics don't have anything like the breakdown and varnishing problems of older oils. So if that is the limiting factor, you can run oil for a long time without changes. If, on the other hand, the limiting factor is buildup of combustion byproducts, the newer oils are only a little bit better than the old ones at keeping the junk in suspension... and it still builds up.

If you don't do the analysis, you never know. And if you don't know, it is best to play it safe. Oil is inexpensive. Engines are expensive.

--scott

Totally agree, Brian. There is nothing inherently wrong with top-posting, and I usually find it very convenient to read. There was never any sort of law against it, just recommended practice.

Some people organize their files in folders with the most recent first. Others see it like a book, where the beginning is page one and you file to the back.

At the end of the day, it doesnt make a damn.

byproducts,

Oil analyses are not very expensive, and I guess are better than nothing. I do not have a lot of faith in them.

But you are very right ...lubricants are inexpensive and engines are very expensive. Premium filters are dead cheap (if we can find out which is a premium filter and which is an old sock) in the scheme of things.

On the other hand, they're starting do do a very few things poorly. Most modern engines lack a few friction mechanisms that were present in older vehicles: modern cam followers are almost exclusively roller type, which eliminates the extreme pressure point of a flat tappet sliding on a camshaft (the highest pressure wear-point in an engine so equipped.) Modern engines also typically don't have any gear drives at all, where as almost all older engines had at least a helical gear-driven oil pump and distributor and a few had gear-driven cams as well.

Both flat cams and gear drives require certain additives to protect them properly, and these additives are DEcreasing in concentration in newer oils. They're also "depleting" addtives that are actually consumed from the oil as they do their job. Fortunately, there are still formulations around with plenty of those additives that can be used at extended drain intervals in older engines (Mobil-1 High Endurance, for example, which is why it receives an outdated API rating- it has too much of some additives to qualify for the latest rating).

Oil isn't a "one size fits all" choice.

Thanks to all of you for your interesting (and mostly applicable) inputs. One thing my mechanic mentioned to me, and which I didn't see mentioned in your posts, was that data he saw showed that synthetic oil reduces friction over dino oils, resulting in better mileage (something worthwhile thinking about in these days of $3.00/gallon gas). Have any of you seen data to back that up (or refute it)?

Jim Thomas

I have had people measure their mileage before and after changing to synthetic, and swear that they get a little better mileage. I believe I have seen some test data that shows a little better mileage can be expected in some conditions, but would have to search to find the report.

I think it is probably true, in some cases.

It could be true. But physics don't change at this *level.* Most of the energy expended by the gasoline goes into overcoming the inertia of the vehicle, and wind resistance.

I think people can get better mileage just by being sure their tires are properly inflated. IOW, I wouldn't switch to synthetic -just- for that reason alone, unless I could be convinced it would pay for itself with the money saved on gasoline.

Lg

Yes, and that's becoming a problem. I have heard of a few cases where folks used modern synthetics on small engines with splash-plate oil systems. The improved flow characteristics of the synthetic oils means the splash plate can't grab any of the stuff to fling it up, and the engine is quickly ruined.

I don't know what the high pressure characteristics of any of the new synthetics other than the Royal Puple stuff are, but the data sheets on them ought to have three-ball tests, and they shouldn't be any _worse_ than an older petroleum oil. On the other hand, why spend more money for something that is only just as good?

And, of course, the ability of the synthetics to flow through tiny spaces is a good thing from the standpoint of solvent action and getting varnish and gunk out, a good thing from the standpoint of lubrication, and a really bad thing when it turns tiny gasket gaps into huge leaks.

--scott

I think the mileage improvement due to reduced friction is going to be so small it'll be unnoticeable. On the other hand, the improved solvent action keeping your engine cleaner might improve mileage also.

--scott