How often to change Synthetic Oil.

[Z15]

You can switch to a synthetic at any mileage providing the engine is in good mechanical condition. Switching to a synthetic will not hurt anything BUT will it be cost effective to switch at that many miles? One of the many benefits of synthetic oils are that the prolong engine life But in reality many engines with that amount of miles have seen their better days.

Installing new synthetic oil in a high mileage motor may not be able to handle the left over sludge and deposits, and the new lubricant soon becomes dirty with all the deposits and possibly sludge left behind from years of using petroleum oils. I would recommend that you use a engine flush product to clean out the engine prior to adding new oil such as a synthetic. There are several on these on the market, Something like this.


There is no reason that you cannot switch back and forth, that is myth that you cannot do that. Oil is oil, the engine really can't tell which is being used.

 

[Eagle]

cheaper than that is 1 quart of ATF.

 

[Z15]

That's an oil mechanics myth, born out the usual obsession to find something cheaper. But in reality, ATF is not recommended to be used in an engine no more that engine oil should be used in a automatic transmission.

ATF is just hydraulic oil and contains very little detergents compared to motor oil. Engine oil is formulated to have very low friction properties while ATF is formulated with high friction properties for the clutch pac's in the trans to function. Dexron type ATF has a viscosity in the 5-7 range (VI-III) so it a very lite hydraulic oil and because it is thin, people think its doing something good by adding to the engine oil. But the average qt of engine oil has much more cleaning abilities that any qt of ATF.

IMO putting ATF in the engine is liking play Russian Roulette. Especially with modern ATF's. Back in the old days, they were not that far apart but today contain many different additives that can be harmful to engines. Dexron VI is not even recommend for manual transmission's that have used ATF in the past because they can be harmful to seals used in those gearcase's.

 

[Eagle]

actually it has dispersants which help keep contaminants suspended while draining the oil.
No one says to drive around with atf in the crankcase.

it is a much better lubricant than KEROSENE/Diesel (though poorer solvent of course) which is the genuine OG way of doing it, and is the main ingredient of many engine flush products.




These vehicles are new enough that the oil used shouldn't have formed any deposits if changed regularly. Plus the capacities are large enough, and the oil cooling ability high enough, that the oils should NOT have had sludge problems, unlike certain 3.5 quart of oil v8s from certain import manufacturers.

Switch to synth if you want with no 'prep' needed. I noticed a bit more noise during cold weather start ups, as compared to dino. Now that the weather is mild to hot, no noise.

I also noted a small change for better mpg. nothingmajor but enough to pay for the extra cost.

jsut not happy about the undersized filters.

 

[dropmech]

The computer is a good guideline, it uses hours, rpm and load to calculate oil life expectancy.

Until the computer resets the hours on you unexpectedly as it did with mine. I have 47 hours on my hoe with 80k miles on it now. That averages to just over 1700 miles an hour!

 

[Eagle]

That is AWESOME.
has tp be the fastest Tahoe on the boards!
I am sure you remember about when you changed it, so do the ~4 months change or 5,000 mile change.

 

[ypsetihw]

in my 1.8t 4 cyl jetta I use mobil 1 0w-40 and get near 10k to the oil change . . . it all depends on how much you wanna invest. go to midas and get an oil change for $20, and you prolly need another change as soon as you pull outta the parking lot. on the other hand, put some good mobil 1 synthetic and a better than OEM filter, and you'll get 5k+ no problem.

in the long run you'll save money with good oil because you won't foul the engine as much and you'll have to change it less often, which more than offsets the added cost