My 1997 S70 (non-turbo 2.5, 20V) has started burning 2 ltr of oil between oil changes (10,000km intervals) after 290,000km. I never had to top up engine oil between changes since new. I use full synthetic oil. I read that 15W40 would be the right oil to use for high mileage engines like mine, some say 15W50 or even 20W50 should be used, while others say 10W40 should be fine. I am confused. I live in warm climate where it never gets below 0degC. Any suggetsions? Thank you

 

I'd go for the 10W40 this oil change and see what improvement you notice.
That way if you do get any colder weather your better able to handle those temps as opposed to 15W.
I assume you were previously using 5W30 ?

 

that is not unreasonable oil consumption. If you move to a more viscous oil it will wear to that oil as well. I'd stick to what you are using now. I prefer 5W-30 . Just put in a liter midway between changes. By the time you get to the 2nd liter, it will be time to change the oil.

For trivia, Honda considers 1 quart /1000 miles as acceptable oil loss.

 

The owners manual warns against using 15w-40. I use 10W-40. Oil consumption may not be from motor wear, it's likely from a clogged PCV system. Blowing the oil out. You can do a compression test to see if the motor is worn.

 

Which synthetic oil are you using? Hopefully not Mobil 1

 

I happen to like Mobile 1. It's relatively lower cost and it works. The MB requires it at 0-40 and I can get it at Walmart for <$30 for 5 qts. There are lots of oil brands that advertise better and I am sure they are indeed better but the price tag is bigger too.

The bigger question is why use Synthetic. There are consequences to switching to synthetic. These cars are at 13+ years old and did not start with synthetic oil. You are far better off using a dino oil on older cars or at least a blend and changing it more often.

 

Hmm...my 1995 Pontiac Bonneville had 122k on it when I picked it up, used conventional and I did so for a while. At 150k I switched to AMSOIL and did 15k mile/1 year oil changes since then...at 211k the transmission died and I drove it, in 1st, at 40mph nearly (4000rpm) for 30 minutes without issue. It's a misnomer about switching to synthetic after a car "has had dino oil all it's life", it's metal parts that have certain gaps and require oil to lubricate, nothing more...there's no memory nor is it like a human and will get "pissy", a transmission on the other hand, had umpteen seals and so many different parts that yes, a change in fluid viscosity can affect it, especially (and most usually) if it's already on it's way out. The transmission relies on the very modulated pressure to do it work, all you are doing with oil in an engine is lubricating and protecting.

 

I will also tell you while you are certainly right Mobil 1 is cheap, and yes, there is far better on the market...as far as synthetics go it's almost a waste...I've seen so many people lose their motors to it...it used to be good when it had zync and other additives in it, then they cheaped out...it hit bottom of the list for a good long time, it's starting to come back but after what they did I still wouldn't trust it (nor do I with the stories I read). The only synthetics right now I'd touch, and recommend, are either Royal Purple or Amsoil. Realize that when you compute the mileage you can put on either vs the mileage allowed per dino oil change and cost of the changes, you SAVE money and it's CHEAPER to use either AMSOIL or Royal Purple, cheaper than even Mobil 1. Unfortunately people can't see past the initial price tag of the oil and realize that it's cheaper per mile.

 

My brother is a Royal Purple guy. He also makes 10 times as much money as I do monthly. LOL I believe the main stream full synthetic oil is better than using dyno.

This is my take on it:

 

Thank you all for your suggestions. I have been using 5W30 lately but early on it was 0W40. Most of its life I have used Mobil 1. I will go with 10W40 from some other brand since Mobil does not sell 10W40. As the ABS is also playing up, I do not want to put very expensive oil as I am not sure if it is worth spending too much money on an old car. Having said that, it still runs very well, and I never had any problems with the motor, transmission or electrics, and is extremely reliable.

 

Nothing wrong with going semi-synthetic if costs are becoming a little bit prohibitive for you.

 

It was the point of what I wrote. Unless you are keeping a 13+ yr old car for a long time, spending lots of money on oil is a waste of money. Especially when you look at the likelihood of a blown head gasket and burnt valves, etc.

I use Mobil 0W-40 on the Benz because it's the only oil that meets their spec. It comes in 1 flavor and it's a specific european blend. But its $8K if that motor lets go so I follow the manufacturers recommendation. I say that even though I think that any oil that starts with a 0 is not a good idea unless you live somewhere really cold. I live in the North East, I go for 5W-30 because it gets cold here. If you live in FL, TX, Az, places like that, 10W-40 is a good weight. The first number is the weight when cold, you want a number that allows the oil to pump and flow when you start the engine; which is why 15W anything is not a good idea. Buy a good quality oil. If you buy dino oil, replace it like a religion at 3-5K miles. If it's synthetic, run it 7.5-15K miles (though i believe in a mid cycle oil filter if you go over 7.5k since synthetic holds particulate in suspension).

I never pay attention to the high end manufactures oil hype. The hype is justification to get you to pay lots of money for their product. I've aged some and I don't wind the engine up near the redline anymore. RSPI has a vehicle that went several hundred K miles. I've personally owned a few cars that were in the 200-300K mileage range that I got rid of because the rest of the car was worn out. In fact, the Suburban I had went 275K miles before I got rid of it and it burned 1.5 qts of oil between changes. It burned 1 qt of oil between changes when it was new. I think I ran quaker state 5W-30 full synthetic for the last several years I had it.

Don't change the oil, or filter or wait too long on it and the engine is junk, regardless of the oil you use. Some people don't do it and they pay the price for it.

 

I'm not sure about the studies here...but i don't remember the manual calling for a x w 40 anything? That means the oil is getting THICKER than what the engine is designed for, meaning decreased flow speed...more resistance...that's not technically good. That's like people that think 0w x vs it calling for 10w x...yes...it flows UP to the top faster on initial startup but it's like using water vs honey to protect your engine. Think about it, logically...it's common sense. I wouldn't go putting a w40 in a w30 spec'd motor...ever. If you need to do that, it's a band-aid, and it's not going to last long (you should be looking for a new motor at this point)

 

I don't think another $10 per oil change is a lot of money unless you are driving 5,000 miles per month. Also, if you are running full synthetic, you can go longer between oil changes so the cost will offset.

The way the rest of my car is holding up, I think I'll be driving this car for another 5 years. It has great features, it's very reliable, I don't mind fixing things, I'm able to fix things myself so, I think I'll enjoy it for a while. (Not to mention I can't afford to purchase a newer car). I'd much rather have this OLD Volvo than some other old car that's falling apart.

 

Not to mention these Volvos are built a lot better than most of what's on the road...and the ease of working on it is great.