Extended Oil Change Intervals And Engine Life

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Jan 16, 2003
Southern California
If you got this far, don't blame me if you don't like the challenge. I spelled it all out in the subject line. This is really a poll because I'm curious. What are people's experiences with extended OCIs (more than the typical manufacturers' advice of 7,500 miles under "normal service") <i>vis-a-vis</i> engine longevity. I'd appreciate honest responses of the intervals and what, if any, engine mechanical malfunctions that might conceivably have been attributed to the oil, and at what point in the engine's life they occured.
Amsoil dealers should jump in here, as I know from reading the Amsoil literature in the past that there are many Amsoil customers who get well over 300,000 miles from their engine using super long drain intervals. As long as you're using UOA to determine your safe point, there is no reason you can't get long engine life while doing 10k+ OCIs with a lot of engines.
I'd rather avoid chapter and verse quoting of oil manufacturer literature. I feel anecdotal evidence from the membership, though unavoidably biased on a case-by-case basis, would be more informative, since the pure numbers (the more the merrier!) would indicate trends.
Ray, I just bumped this Castrol GTX High Mileage 10/30 to the top in the analysis section . Might not need those expensive oils if people would leave their oil in longer than some do. Nothing hidden here this is raw data :)and no engine problems from it. Brings new definition to [Smile] " High Mileage Oil " [Smile] huh ? A 10k mile dino motor oil below --------------------------------------------------Changed oil in friends 1998 Hinda CRV 2.0l 4 banger after she said it had been about 6 months since her last oil change. Oil has 9,403 miles on it with NO, ZERO, I mean NO makeup oil. I had a few OAI sample kits around so I took a sample of what I thought would be abused oil. BTW this was w/ a TINY PureOne filter. Iron=12 Chromium=2 Lead=8 Copper=13 Tin=0 Aluminum=6 Nickel=0 Silver=0 Silicon=11 Boron=2 Sodium=11 Magnesium=64 Calcium=1908 Barium=0 Phosphorus=1145 Zinc=1304 Moly=40 Titanium=0 Vanadium=0 Potassium=0 Fuel <1 Water NONE Soot/Solids NONE Glycol NONE Visc100=13.07 Oxid=47.0 Nitr=41.0 TBN=2.41 OAI advice was oil is suitable for continued use. BTW she drives about 50 miles a day highway round trip for work. [ November 14, 2003, 03:32 PM: Message edited by: Patman ]
I think 3mp's study has shown that extending OCI's mean absolutly nothing as far as increased engine wear when they are accompanied by UOA's. wear in PPM is higher than a 3k or 5k interval (quite a few US built vehicles still have the 5k "normal" service OCI), but that is only because the oil was run longer run 3x longer & get 3x the wear - it all works out. I personally think that running a quality synthetic (grp IV/V) for extended OCI's vs. a quality dino (grp II) at 3k OCI's will potentially increase engine life due to less sludge build up. Then inside of the engine will be cleaner - therefore supplying better lubrication flow and extending engine life. And, don;t forget that many people running 3k OCI's don't do occational UOA's while many people running extended OCI's DO use UOA's and are therefore more likely to find other problems before they become leathal.
Ran a 1985 Merc. Topaz on a steady diet of M1 10W30 and Fram filters (pre-BITOG) with 10K oil changes and gave the car away to our daughter with 240,000 miles and it didn't burn a drop of oil and the valve cover was never off. It's a 2.3L 5 spd manual car. DEWFPO
I medic brings up a good point about sludge build up. Sure, wear metals (total) over the life of the car will be the same after 200,000 miles (or whatever) (3K dino vs 10-20K synthetic) - but the waste oil generation alone should cause one to hesitate. Now with more and more car makers going to 7500 mile + OCI's (for bragging and enviromental reasons) - synthetic oil just starts making more and more sense. [ December 14, 2003, 03:37 PM: Message edited by: Pablo ]
I've been averaging 12,000-15,000 mile drain intervals for the past 25 years and I haven't come close to wearing out an engine. A case in point is my 1990 Audi 100, which has had 15 oil changes in 212,000 miles and it still in excellent shape. I've had similar experiences with seven other vehicles using Amsoil over the period from 1978 to the present....If I had used slightly shorter drain intervals of say 10,000 miles, perhaps the results would have been even better, but my engines are outlasting the rest of the vehicle as it is. If you drive over 25,000 miles per year, I'd use both an ACEA "A3/B4" quality synthetic oil and a bypass filter, w/ yearly oil analysis and filter changes .... That is the ultimate set up in terms of optimum engine life and low maintenance ....
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