CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

To change or not to change to Synthetic oil

I have a 2002 Grand Jeep Cherokee Limited - 4.7 HO engine - 127,000 miles - non oil burner or leaker. I live in Cabo San Lucas ( Mexico). I’ve changed the oil & filter every 3000 miles since I bought it new. As I now live ( 7 years) in a high dust, heat environment, would there be any benefit / harm to switching to synthetic oils at this point. Engine still performs like new, 19 mpg @ 65 mph in 90+ degree weather. Thanks in advance. Rick

Unless you plan on extending your oil change interval to 7500 miles, there is no benefit that I can see. If it ain’t broke, then why do you want to change?

I agree with keith. You said it yourself: “engine still performs like new”.

FYI, high heat and high dust are not factors for your oil. You engine is well sealed against the dust and the cooling system keeps the oil temperatures in a warmed up engine to about the same as they would be in Alaska in the winter, unless you have an add on oil cooler.

Your oil change program is plenty adequate. You need to concentrate on the air filter and the cooling system. Use a long life antifreeze at 50/50 and change it every 5 years. Do not flush, just drain and refill.

Since your Jeep is now ten years old and if you are about due for a coolant change, I would suggest that you look into replacing all the rubber hoses, radiator and heater, put in a new thermostat and a new radiator cap. Use a premix long life antifreeze or if you mix your own, use purified (RO) or distilled water.

Drain both the block and the radiator and do not be tempted into flushing out the block with a garden hose. NEVER use a chemical flush either. If you have been maintaining your cooling system anywhere near the factory recommendations, it will not need any kind of flushing. Flushing introduces contaminants that I believe will shorten the life of the cooling system.

Sincere Thanks!!! to all who took the time to provide their advice so quickly.

Yes, I have maintained the cooling system, air filter and all other systems as per factory recommendations including keeping the engine itself and it’s compartment cleaned. A mechanic has no complaints when I raise the bonnet. I did perform a cooling flush perhaps 7 years ago prior to towing a trailer from Virginia to Cabo and have not experienced any problems related to it, although did loose a heater core about two years later - I replace the thermostat and cooling fluid annually. The Jeep has a wonderfully dependable vehicle with reasonable repair requirements all considering I’m no sissy driver and it does go off-road on a regular basis. When we leave this area for a less harsh environment, I will replace it with a new one.

Keith: I’m curious. What is the concern with flushing a cooling system with a garden hose?

You can switch between synthetic and non-synthetic oils back and forth at will. I personally like synthetics and think they’re worth the extra money, especially in extreme temperatures or severe service environments (like taking your vehicle off road all the time)

The expense isn’t much more–why don’t you try a good synthetic? Mobil-1, Valvoline Synpower, Pennzoil Platinum, and Castrol come to mind, though there are really pricey ones too like Royal Purple and Amsoil if you go that route. Try it and see if you notice any difference in the way the vehicle runs, your fuel mileage, how clean the oil stays, etc. Then you can debunk the synthetic oil myths yourself.

JoeMario, it allows contaminants from the public water system or well into the system. You can argue whether these are significant, but I’d just rather avoid the issue. I really don’t like those chemical flushes, everytime I used them, I had leaks in the cooling system shortly after. I stopped using them and I haven’t had a problem since, except one heater hose that oil dripped on.

Thanks Keith. That’s interesting. While I too don’t like or use chemical flushes, I don’t think I’ve ever not used public or well water in a radiator. And I can’t remember the last time I saw someone use purified or distilled water.