Group 4/5 Synthetics Cleanliness and 6k intervals

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Nov 26, 2002
Texas & BWI Area
Suppose you take a premium conventional oil Delvac 1300, Delo 400, Chevron Supreme XW30 etc change it at 3-4k/ intervals. (daily driver, highway/street driving)

Then on the other hand running Mobil 1, Amsoil, GC, RP, and RL on the other hand at 5-5k intervals. (or 8-10k depending on UOA).

My million dollar question is at what mileage interval can synthetics maintain OPTIMUM engine cleanliness?? (on a non bypass filtration system that is)

My first going assumption is that by a certain mileage the oil will be holding its capacity of chemical contaminants and microscopic abrasives.

Second, going assumption is that as the sythetic ages so will the likelihood of deposit formations.

The dilemna I have been pondering has been 5k on synthetic may not be as overkill as thought of.
They ran a synthetic oil long term study (not too scientific) where they ran Mobil 1 18,000 with a filter change at 12,000 miles. The oil was in grade and maintained enough of it's detergent package to still be effective at 18,000. An oil analysis was done at 1,000 mile intervals to be sure the oil was OK.

They are now running Amsoil in the same car and are up to maybe 10,000 miles and the oil is doing OK, though the TBN is getting very low.

I run Mobil 1 at 10,000 mile intervals and I use a Purolator Pure one filter. 150,000 miles and still running strong. No oil analysis so I could be changing too soon, who knows.
Mobil 1 has run test in the past and probably in the present where they have run vehicles at 7.5K oil changes and 15K mile oil changes and at 200K miles the engine was exanined and found exceptionally clean. Based on what we see here I'm starting to have difficulty with totally believing the 15K change interval. But it does seam that you can go at least 7.5K changes with full sysnthetic and have little deposits for as long as you are gonna own the vehicle.
I have been running 15,000 mile oil and filter (fram, no less on a TLC sold at app 250,000 miles) intervals for a total of app 660k miles, on Mobil One 5-10w-30.

I am also running a 10,000 mile oil and filter change intervals on an VW TDI engine (under warranty till 50k, but am on 36,000) and will in all likelyhood switch to at least a 15,000 mile interval when the warranty expires with Mobil Delvac One 5w40 aka Mobil One Truck &Suv, which is backward compatible (viscosity notwithstanding)with the SL gasser standard. The Mobil One 5w30 is not backward or forward compatible with the CI-4 standards.

In so far as cleanliness of the engines, the 87TLC needed mandatory 15,000 mile valve adjustments and the 91,94,96,97 TLC needed measuring at 60k with the possibility of a couple hundred dollar readjustments and not only have I not needed the valve adjustments, the dealer mechanics who have had to get into these motors on a scheduled basis have been saying the adjustments haven't even deviated from new specifications. All have said each of these 5 vehicles had surprisingly clean engines!!

I also run the same intervals on a 2001 Corvette Z06 with app 66,000 miles. From polls of others that have 2001's, I seem to have many more miles than most owners.

Again if there are any doubts on either the conventional or synthetic, spot,periodic or systematic oil analysis can remove them. This thread is a real help in that you can also compare them with folks who use like engines or close to what you run to compare yours with others folks experiences.

[ August 08, 2004, 12:45 PM: Message edited by: ruking77 ]
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