[sarnali2]

I use Mobil 1 15-50 car oil in the engine and change it and the stock oil filter every 5k, for the trans and primary I use Mobil 1 75/90 synthetic gear lube and change every 10k. In my Suzuki I use Shell Rotella T 5w40 full syn. and change every 5 k and the gas-guzzeling SUV gets Mobil 1 5w30 extended service full syn. and gets changed every 15k. I'd use Rotella T in that too if they made a full syn. 5w30 weight.

The weather here is mostly cooler with only a month or two of 80's and 90's. Oil and tires tend to last longer than hotter parts of the country, so IMO short oil changes are a waste of money.

 

[sarnali2]

Every 15k for an oil change on an SUV? Isn't that a bit extreme? .

Not really, the recommended oil change interval is 7.5K with dino oil, synthetic oil doesn't break down so it's really the oil filter that determines how long to go. Mobil states that their extended service oil is good for 15k and they warranty against any oil related failures using their product so that's how long I go. The oil does get "dirty" but that's what the filters for, I use either the high end Purolater or stock Ford FL820S

Long haul trucks go upwards of 150k on their oil in hi compression-hi temp turbo diesels, true, they have multiple filters and they do oil analysis to determine the state of the oil but I figure 15 k in a modern standard gas engine is fine.

The 3k oil change interval is from the stone age of less complex oil matrix's and less precise manufacturing tolerances, leaded fuel and less efficient combustion. I think it's a waste of money and rescources to follow that in a modern gas engine.

It is of course entirely up to you how often you change your oil and I'm not saying anyone should do as I do, however reading up on oil and oil change intervals convinced me short oil changes in a modern engine was unneccessary