Oil change intervals?

[cn90]

Re Oil Change Interval...

For a new car, I think synthetic and every 5K is fine.
This is what I have been doing for years, but I just did the oil change in my 1998 S70 GLT with 165K, the oil is dark and a it thick after 5K.
I wonder for older engines (more combustion byproducts in the crank case), should we reduce the interval down to 4K or even 3.5K?

[benrk]

Re Oil Change Interval...

For a new car, I think synthetic and every 5K is fine.
This is what I have been doing for years, but I just did the oil change in my 1998 S70 GLT with 165K, the oil is dark and a it thick after 5K.
I wonder for older engines (more combustion byproducts in the crank case), should we reduce the interval down to 4K or even 3.5K?

I wouldn't be concerned, if the oil is black, it means the detergents are doing their job & prevent the soot from depositing in the engine.
As far as combustion byproducts which are mainly gaseous are concerned, I'd rather kerp an extra eye on the PCV which is tasked with removing exactly those gases from the crankcase.
Remember, even the 5k mls interval in '98 was spec'd with different oils & fuels, even here in North America we now have ultra low sulfur fuels & if you're using high quality full synthetic oil that in Europe nowadays is used by many manufacturers for 24months/20k mls (some longer) oil change intervals, I really wouldn't worry about 5k mls.

The 3k mls oil change ferry tale imho is an oil industry scam.

[reverend]

Ayup. Oil usually gets dark real quick, so changing oil on color would mean changing it every 1000 miles. hehe

I have a 2006 V70 2.5t with 120K miles on it and with Mobil One full synthetic, I changed last at 10K miles and did an analysis and everything was well within limits. I have a 30 minute commute each way so the engine gets up to temp every time. Previous owner changed every 3000 miles with Castrol regular oil but he drove 40 miles hwy each way to/from work, so that kept the PCV very clean. I still changed it at 109K since I had it apart.

The 965 (whiteblock 6 cylinder) was fine at 15K oil changes, again, Mobil One full synthetic. I had it analyzed and it surprised me.
I'm *tempted* to go 15K on the V70, but being a turbo I'm hesitant. We'll see when I get to 10K what I feel like.

I wouldn't be concerned, if the oil is black, it means the detergents are doing their job & prevent the soot from depositing in the engine.
As far as combustion byproducts which are mainly gaseous are concerned, I'd rather kerp an extra eye on the PCV which is tasked with removing exactly those gases from the crankcase.
Remember, even the 5k mls interval in '98 was spec'd with different oils & fuels, even here in North America we now have ultra low sulfur fuels & if you're using high quality full synthetic oil that in Europe nowadays is used by many manufacturers for 24months/20k mls (some longer) oil change intervals, I really wouldn't worry about 5k mls.

The 3k mls oil change ferry tale imho is an oil industry scam.

[regent]

I remember how surprised I was to see (for the very first time) the colour of the oil draining from a diesel engine many many years ago... It looked 'darker than black' (and so did my hands during the next couple days)