lavamadness

Apologies if this has been posted before....
http://neptune.spacebears.com/cars/s.../oil-life.html

Damon

I'm an Amsoil dealer but I only sell to myself so I have no axe to grind (I like the discounts and I do a LOT of oil changes on family member's cars). Here's the straight skinny: 7500 miles is a long as you would want to go under "normal" conditions between oil changes- synthetic or not. Synthetic oil lasts basically forever, chemically speaking, but IT STILL GETS DIRTY!!

If you run a standard parts store spin-on oil filter 7500 is a good benchmark. The filter can't filter down small enough to provide good protection from real tiny particles that can damage your bearings long-term. If they made the filter fine enough to filter them all out the filter would become clogged rather quickly.

If you want to go beyond that then Amsoil recommends a "bypass filtering system" which is a rather complicated set of coarse and fine filters (externally monted in the engine bay) that CAN take the filtered particles down to about zero. With this system you can run effectively FOEVER without ever changing your oil IF YOU SEND THE OIL FOR TESTING TO AMSOIL AT REGULAR INTERVALS. They will analyze it and let you know what, if any, additives you need to add and if you need to change either of the filters. Etc, etc. I know one guy who has driven his F-150 for 180K miles without EVER changing his oil using this system. Most people change their oil every 25,000 even if they ARE using this sophisitcated bypass filtering system. So you might have heard numbers as high as 25,000 miles- this is the reason why.

I myself change the oil in my daily drivers every 10,000 miles using regular spin-on filters and Amsoil full synthetic 5W30. I push slightly beyond the 7500 mile recommended change interval becuase I do 90% highway driving which is much easier on the oil in every way than lots of stop-and-go or driving in dusty conditions.

My 1991 GMC Jimmy has 204,000 miles on it using this regimen ( my daily driver that I drive 30,000 a year).

My 1994 Firebird had 130,00 miles on it, likewise.

My wife's 98 Jeep Wrangler has 60,00 miles on it and the oil's only been changed 5 times with Amsoil synthetic.

Synthetic costs 3X as much as part-store oil. But it lasts 3X longer. DON'T put it in an engine that leaks oil like crazy- that's wasted money.

Damon

In the interest of fairness I should mention that Amsoil, Mobil 1 and several others like to bad-mouth eachother, each claiming to be superior. I have no idea what the real truth is. Both Amsoil and Mobil 1 are quality products in my extimation. Both put out products that are about 5 billion times better than you'll ever need your motor oil to be.

25THRSS

Good info. Very interesting.

ede

10,000 miles on an oil change, i go 3000 miles or 3 weeks which ever comes first, but i drive a lot.

Tom84L69

Even owner's manuals on newer cars say you can go up to 7500 with regular oil and freeway driving. I usually go about 5-6000 on my Trailblazer on regular oil. Of course it is a lease so I don't care about longevity.

Damon, amazing miles/oil changes.

I only run synthetic in my race car (an SCCA Triumph Spitfire) to keep temperatures down and since it's British it leaks enough oil to give itself regular changes.

Acidtalons

A friend of mine works for the US military repairing/servicing Bradley and Hummer chassised vehicles.

They use a similar system to the one that Damon described and send the oil out to be tested every 6 months. Some of the vehicles he services on a regular basis have been using the same oil for as much as 3 years. However these are much larger diesel engines that take alot more oil than a regular car ( The Bradley has a 10 Cylinder Turbo diesel that uses 14 quarts), so I would still change my oil on a car every once is a while even with a complete filtration system.

Synthetic oil is vastly superior to dyno oil, but also much more costly.

five7kid

iTrader: (14)

From a cost standpoint, what's the difference between using synthetic in an engine that leaks or consumes it, and requires more frequent add-oil, and changing the oil before it needs to be changed?

I've been using AMSOIL since June, 1983. They recommended 25,000 mile/1 year oil changes back then if you used their air and oil filters, oil filter change at 1/2 the oil change interval. With the by-pass system, change the filters once a year, and the oil when analysis indicates it is needed (typically relates to a non-oil failure such as antifreeze contamination, rather than the oil being used up). Keep as much dirt as possible out of the oil (read: good air filter), filter out as much as gets into the oil as possible (read: something better than over-the-counter oil filter), and the oil will last a very long time. Add-oil for usage replacement and filter changes will replenish the additives.

Only thing that's changed since then is they now have a couple of oils that can go 35k/1yr with their air & oil filters, oil filter change still at 1/2 oil change interval.

These test results are no surprise to a very many of us. Interesting that Mobil has backed off their former extended drain recommendations since they "merged" with Exxon.

(Yes, I'm an AMSOIL dealer. Primarily for my personal use - 6 vehicles on the road right now, also family members, and anyone else that's interested. I don't pound the streets looking for customers. I'm not looking to convince anyone to switch so I can make money. I've got something good [read:information], and I want to share it.)

25THRSS

I think it will be very interesting to see how their study of amsoil stands up to the mobil 1. I will definitely be adding this to my favorites and checking it to see the results. Looks like the mobil 1 has still stood up and is actually getting slightly better after 13,000 miles!