right up cary's alley --

Mar 28, 2003
I found this on the M1 site --

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Which Mobil 1 For A '95 Saab In Wisconsin

Q: My 1995 Saab (2.3L non-turbo) recommends oil weights between 5W-30 and 10W-40. The owner's manual states that 15W-40 may be used, but not in winter. My intent is to set a personal high-mileage record with this car, so I want ultimate protection. I am considering using Mobil 1 0W-40 in the winter, and in the summer a mix of one quart 15W-50, two quarts 0W-40 and one quart of 5W-30. I know that the stock answer is to follow the owner's manual, but Mobil 1 does not have a 5W-40 or 10W-40 that would give me the greatest high-temperature protection in a weight specified in the manual. Do you see any problems with my strategy, considering that engine longevity and not warranty compliance is my goal?

-- Jeff Peterson, Pleasant Prairie, WI

A: While there is logic to your assumptions, mixing various grades of motor oil is not a sound strategy. Although all of the Mobil 1 viscosity grades that you mention have a similar formulation, you simply cannot assign a predictable SAE viscosity number to the mix that you are suggesting. According to our information, Saab recommends 10W-30 in your car for all temperatures, so we would suggest that you use Mobil 1 with SuperSyn in that viscosity. However, since you are specifically looking to optimize both low-temperature winter protection and want maximum durability in the summer, you can use Mobil 1 0W-40 in the winter or all year round, and you will still get SAE 40 grade protection. Alternatively, you can switch to Mobil 1 15W-50 for the summer only, but if you use 15W-50 in the summer, you must switch to a lighter grade in the colder months.
May 7, 2003
I would agree with Mobil. Ow-40 is designed to fulfill the requirements of 15w-40, 10w-40 and 5w-40, and for his SAAB is probably the correct weight. The guy by mixing three different grades is accomplishing nothing. I don't normally like mixing oils, but if M1 5w-30 or 10w-30 is the only available grade, adding a couple quarts of 15w-50 will help bring it from a low 30 weight oil to a high 30 weight.


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