Originally Posted By: VeryNoisyPoet
Thanks for all the replies so far!
I understand that I won't see instant cleaning, and that slow dissolving of deposits is better than dislodging clumps.
Well, oils CAN dislodge lumps.
I had that happen to my 900 GLE. But then, this car has had a history of extrene neglect. (At least two of the previous owners were women. Coincidence?)
In your case, that should be
extremely unlikely.
Quote:
I get that 10w-30 is acceptable down to 0F, but the car does see a lot of short winter trips and I wonder if that (plus the even higher viscosity of the HM version) will eat some of my fuel economy while warming up. It slurps enough fuel when cold as it is. And running it on the coldest range of what it specs for 10w30 rubs me the wrong way I guess.
But VIIs getting roasted by the turbo is a valid concern.
I really don't get why BITOG people are so scared of shearing VII. In a good oil, they don't. I have
four UOAs of 0w-40 coming out of a
1980's turbocharged engine after 10.000km in essentially virgin condition.
When your viscosity and viscosity index drops, most likely it's fuel contamination. And there is only one remedy to that: Short OCI. (Besides the obvious: fixing injection problems, checking air mass meter and lambda sond, and of course avoiding short trips.)
The biggest levers to improve fuel efficiency are driving profile and driving style. On my Saab, I can make a tank last 880km - or I can burn though the same fuel in less than 300. (Here is a link to my
spritmonitor profile. Look at the extreme variance in fuel consumption. Some tanks have even been flagged "invalid" by the algorithm and excluded from the averages, because they seem so excessive.) Worst offender in this regard was
my 8V turbo: on a swedish country road, or just setting the cruise control at 89km/h following a semi on the Autobahn, it would reliably drink less than 7 litres/100km. But once, I managed to triple that (four and a half hours of near constant full throttle and two refills).
And those cars, that with my usually relaxed driving style would get down to and in perfect conditions even below 7 litres are impossible to get below 10 in the city. End even those are only in good conditions - avoiding rush hour and trying to drive efficiently. Less fortunate circumstances or a less concentrated driver, and 12 is much more realistic.
Of course there are fuel savings in the oil choice. But the difference between a 15w-40 and a 0w-30 is around 3%. That is next nothing compared to the variance in fuel consumption due to driving profile. Learn some basic hypermiling skills, and you can easily save 20% compared to how most people drive.
Getting back to the oil: if that Volvo was mine, I'd just pour some MB229.5 and Porsche A40 approved 0w-40 in. Nice cold starts and plenty of protection, and no worries about the turbo. But that
might leave open your right flank of seal conditioners. Perhaps look for something with a bit of esther?