OCI's and Turbochargers

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Dec 10, 2003
Hey all, I'm currently running Schaeffers Supreme 7000 10w30 in my '92 SAAB 900 turbo. I am thinking that 6k intervals are not excessive, but in light of the added stress produced by a turbo I figured it best to come here for some good opinions.
Amsoil recommends 3X the mfr. recommendation for severe service on turbo cars. This works out to be 10K miles on my Volvo turbo and seems to be a valid number via UOA's. Maybe go 7.5K and run an analysis.
You're probably OK, but I'd have a UOA done after 6k miles (for the first two runs) to reassure myself. Others have said it's shown well in UOAs here, so you might even be able to go a ways longer. I'm running 10k mile OCIs with M1 0W-40 in my '99 9³.
Originally posted by Eiron: I'm running 10k mile OCIs with M1 0W-40 in my '99 9³.
Eiron, what is the displacement/cyl, Hp-Tq output, max boost and sump size of your Saab? Curious as I too have a turbo car - VW 1.8T (chipped). Thanks...
My Mazda turbo has 7,500km OCI's. I was doing 5,000km OCI's but now reverting back to 7,500 with the Visco 5000/RX maint dose/PureONE combo. Hope to get first UOA done on this stuff.
Could be wrong, but my understanding is that most Saabs are low boost and are not so demanding on the oil as some other turbo'd cars. Many turbo cars here vary from 5-10,000 km intervals. Also depends on if the turbo is watercooled. Of course, if you drive it hard then the interval should be set to the manufacturers severe schedule or even shorter. A UOA would help.
The turbo is water cooled, but it is not a light pressure system. Besides, as Eiron will probably tell you, most of us are running higher boost levels than stock.
Bugzii, Our '99 is an auto, so the hp & torque numbers are less than what was available that year with a manual (hey, it's my wife's car). (Honest!!) The engine's a 2.0L 4 cyl with a 4L sump & light pressure turbo (around 8# or 9# boost, I think). Hp is 185 & torque is 169 ft-lbs. (Here are the specs .) I’m assuming your 1.8t is in a Bug? Man, I’d love to have one of those things for commuting! (Although, I’d be hard-pressed to give up my N/A ’90 C900 anytime soon. [Big Grin] ) The owner’s manual recommends using a minimum of semi-syn 5W-30 for 10k mi OCIs ("normal svc," but recent complaints seem to indicate this interval is wa-a-a-a-y too long on semi-syn for this engine). The preferred recommendation is ACEA A3 full syn oil, & in '00 Saab released a TSB stating all cars were factory filled with 0W-40 full syn (it was reported to be "similar to Mobil 1"). Saab’s OE oils have diesel-style additive packages. The car’s not chipped, & I’ve only done minor mods to the intake to increase quickness but not top speed. (My wife freaks every time I make a change to “her” car, but it’s the only turbo Saab I have. [Frown] ) It sees maybe 95%+ short trip service (less than 10 mi), & we’ve had the same 0W-40 in there for 13 mos so far. I think we’ll reach 10k mi in another couple of months. I’ll add Auto-Rx to this oil after I pull a 10k mi sample for UOA, & when I’m done with that I’ll try some kind of M1 0W-40/15W-50 mix. theguru, You’re right, most Saabs are light pressure systems, as that’s always been part of Saab’s engineering philosophy. But, as quadrun1 said, it depends on the Saab! Also, just because it’s water-cooled & LPT doesn’t mean it’s easy on oil. (A Bosch tech rep told me Saab does more to utilize boost than any other manufacturer.) Take a look at the Saab UOAs here & you’ll see they beat up the best oils out there.
Use my OCI formula, with a C* of 60 .... OCI(miles) = (C*)(mpg)(sump-qts)(cubic inches/Hp) Forget the units and just use the raw numbers and that will get you in the ballpark.
TooSlick, I have a question regarding this formula. I ran the numbers for my car, with a 4.8 qt sump volume (counting the filter void volume per the maker's spec), a 122 ci displacement motor, 60 for the constant as you said above, and varied the mpg from 20 (estimated hard use) to 25 (estimated easy use) to get an idea of the OCI range. The results ranged from 3100 mi hard use to 3800 mi easy use. These numbers seem a little low; the maker suggests 3750 for hard use. The car is a Subaru turbo 2.0 and I use Mobil1 10W-30 in winter, perhaps with 1 qt of 15W-50 mixed in for summer. Should I have used a different C value? My car runs 13# or so boost stock. Thanks for any comments.
Eiron - The Hp/Tq output seems right for that displacement and that amount of boost. My NB 1.8T in stock form has 150Hp/162Tq. With the 1.0 BAR chip, APR advertises it at 209Hp/242Tq at the crank. I would say it feels like a 3.0 V6 but without the added weight. I'm with you about the 10k mile OCI being too long, especially if the oil isn't a synthetic. Originally, I used M1 5w-30 and then 0w-40 but now switched to 10w-30 for SoCal winter, which rarely goes below 45*F. For the summer, I mix 2 Qts of 15w-50 to 2.6 Qts of 10w-30 for those long camping/backpacking trips in the Sierra. My NB sees elevation gains of 6-9k ft several times in the summer... and the 2-6 hr long trips in 95-100*F+ heat at engine speeds above 4000 rpm.
Yeah, if I still lived in SoCal & had any turbo, I think I'd only run M1 15W-50 in it all year long. (Or Delvac 1 5W-40, if money wasn't tight.) I've had the 15W-50 in my weakling N/A Saab engine for over a year & it's started fine down to 12°F last winter (straight 15W-50) & down to 0°F this winter (with one liter of 5W-30 used throughout the year for top-ups). I'll go lighter when I change it in another few months. Rotella Syn 5W-40 might be a good winter oil for you if you're not going longer than 10k mi OCIs in your turbo. Half the year on this would also help keep things clean, & the extra anti-wear additives would keep your turbo bearings happy. Heck, this would probably be good for you all year long! How long are you going on intervals?
For Mobil 1, a C* of 80 is probably better .... The best choice for a turbo, is a low viscosity, shear stable, PAO and/or Ester synthetic. The Mobil 1, 10w-30 would be my choice for something at Walmart, followed closely by their 5w-30. You want to maximize oil flow and cooling for the turbo seals/bearings and the cylinder head(s). You also want to minimize high temp deposits from degraded polymeric thickeners. That's why 5w-50 and 0w-40 are probably not the way to go. I'm not at all convinced that ACEA "A3" oils are required for most newer, water cooled turbos. However, also meeting the "B4", TDI diesel spec is an indication of superior detergency/dispersancy. I'd certainly look for that - or "A5/B5" - in a turbo lube ....
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