Could M1 5W30 be to thin at start-up in 100F temps?

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Aug 4, 2003
I live in NJ and drive a Forester XT (2.5L turbo with 12k miles). I took a trip to SC in July running M1 5W30. While in SC, there were a few days of temps in the upper 90's. One day the ambient temp hit 100F. That afternoon, I went to start the car after it had been sitting for two days and heard an awful knocking like the engine was completely dry. Sounded much worse than the normal valve tap some Subies are known for. I check the oil regularly (about three times on that trip) and the oil level was fine. The engine hasn't done that before, and hasn't done it again since. Temps dropped back down to the lower 90's that week. The temp chart in the owner's manual shows that 5W can be used for up to around 100-104F. Is there a chance that most of the oil drained back into the pan since it's thin? Anyone think that a 10W would have done the same Comments appreciated. -Dennis
What does the owners manual call for.Perhaps 15/40 would be better in the summer or all the time .I am not giving you the answer but where to look and when extreams occure weather it be heat index, towing or loaded down thru the mountains,they all require extra protection.I think that they make oils for such uses and just normal conditions like start it up at 70 Degrees drive 15 miles on the highway park it for 8 hrs and do the same going home. The oil market seems to be trying capitalise on our uses by developing as many as they can think of. If I was going on a trip involving extreams and wasn't ready to drain the oil out yet you could add some Schaeffer #132 or drain or suck out a Qt. and add a qt of something like Penzoil 15/40 HD LongLife.This is all I have its your call. [I dont know]
Complain to dealer. The noise you describe is commonly caused by a faulty timing belt tentioner. It is a known problem, your dealer should be aware of it. Most likely it has absolutely nothing to do with motor oil.
Originally posted by MolaKule: If your oil pump lost prime over two days, it wouldn't matter what weight you had in there.
I wonder if it was just one of those fluke things? The manual says 5W30 is preferred (for better mileage of course). The temp chart also lists 10W30 and 10W40. Then it goes on to list 30, 40, 10W50, 20W40 and 20W50 as being acceptable under severe driving conditions (same for most Subes I think). It also says right after the part on 5W for fuel economy that "... in hot weather, oil of a higher viscosity is required to properly lubricate the engine..." Since I also had a trip to Cape Cod, I was using 5W30 to try to squeeze as many mpg's out as I could. The engine is the same as the STi's, but with a different turbo (same as WRX), ECU and intake manifold. vvk - Hadn't considered the timing belt tensioner since I thought that was more of a problem on the older N/A engines. I'll mention it when I take it to the dealer, but it hasn't made even the slightest noise since then. -Dennis [ August 11, 2004, 03:07 PM: Message edited by: bluesubie ]
Do non-energy conserving oils make that much of a difference with mpg's? -Dennis
I had the same experience but with an older model Camry 4 cyl. The car had been sitting for about 4 days and when I went to start it it sounded like the connecting rods were coming out of it. That was 6 months ago. It only did it once in it's entire lifetime. Who knows what it was. It's still running fine though. Bill
Any next higher viscosity oil is going to give you slightly less mpg than the next lower viscosity. However, both Redline 5W40 and Mobil 1 truck and SUV have ample friction modifiers.
Oil pump lost prime? oil filter drained empty? All oil coating the engine dripped back to pan(completely dry, yep)? I wouldn't worry about it. Mobil1 is a good oil. Try a different oil filter. What brand/pn are you using? I'd consider going with something thicker since your manual allows it and it does have a turbo. Concerning MPG, the best way is to test other weights. Give the 0w40 euro, 5w40 trucksuv, 0w30 Castrol, or any other XXw40 synthetic oil a run and see if you actually lost any mpg. I find that MPG varies just as much with gasoline station chosen, tire pressure, alignment, and more so with driving style. Don't forget to use synthetics throughout the drivetrain. This might help with the MPG a little.
A lot of cars do that when they've been sitting for more than a couple of days. It's just takes a sec for oil to get pumped up to the heads when it's been totally drained into the pan. Don't worry about it and move on.
Thanks for the advice folks. I think I'll go thicker next time. Oil filter is OEM and Sube filters are mounted vertically. I'm running Amsoil AGR 75W90 in the gear box/front diff and Redline 75W90 in the rear. I managed to get 25 mpg twice with a cargo box on the roof. Car is rated for 23 highway. -Dennis
I have gotten this before (on different cars) on hot days with thinner oil. I have always assumed it was the lifters/cam followers bleeding out due to the thin/hot oil. I don't think it hurts anything other than making noise until they fill back up.
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