Question about Mobil 1 viscosity.

[Kissfan79]

On the bottles of Mobil 1 synthetic 5w-30, it says that it is a factory fill for the Corvette. On the bottles of the 10w-30, it says that particular viscosity is a factory fill for the Dodge Viper. It the 5w-30 is for "newer vehicles" and the 10w-30 is more of a all around viscosity, why would the Corvette use 5w-30 as opposed to 10w-30 in the Viper. Just curious being as they are both high horsepowered engines.Jim

[esjones]

I have read that a manufacturer will sometimes specify a lower viscosity oil in order to claim 1 or 2 extra MPG in the car's fuel economy estimate. This helps the company's CAFE (corporate average fuel economy) number and allows them to sell more low-mileage cars without penalty from the U.S. government.No idea if this is the rationale behind the choice of 5W-30 oil in the Corvette, but it is a possibility.

[goodvibe]

Actually they are the same viscosity when hot. The high # is the warm viscosity and the low # is the cold viscosity and will only have an effect below 0* at these viscosities. No mileage advantage in the 5w here. The 10w is more shear stable(doesn't thin out) than the 5w because it has fewer viscosity improvers that give the wider spread but break down over time/stress though less so in synth. In the motors mentioned, there is some mileage optimization going on though as they get better wear #s with high 30w or 40w oils and Mobile One 30Ws are on the thin side of 30 to begin with. Even though our manuals say to use 5w 30, it would be better for those in warm climates to use a 10w 30 as it will leave fewer deposits over time. The cold start protection of a 5w is great for northern winters.

[Kissfan79]

With 37,000 miles, would I benefit from switching to the Mobil 1 10w-30? I will be moving to Hawaii soon and we all know about the temeratures there .Jim

[goodvibe]

If it's between those 2 viscosities, yes the 10w30 would be better in Hawaii but i'm not a huge M1 fan. Dino oils like havoline and chevron show much less ironwear in used oil analisis but will probably not keep your motor as clean on extended drains without some help. I'm using Schaeffers blend with Lube Control additive and may try Synergyn in the near future. I've tried M1 in my car and the motor was noisier in general. Royal Purple felt good at first but sheared and oxidized very quickly. I do like their gear oil.

[Kissfan79]

So...are you of the opinion that for shorter intervals such as 4000 mile changes, you feel that conventional oils keep the engine cleaner than Mobil 1 synthetic? When you say your car was noisier with M1, were you referring to the overall engine sound or stuff like the valvetrain?Jim

[goodvibe]

Mostly valvetrain and I dont think either will stay cleaner than the other if you change dino that often and MI half again longer. There are some easy to get oils out there that look to be good. Mobile has just introduced a racing version of Mobile One and Castrol has a 0w 30 made in Germany that does great when tested on long intervals. It's readily available but you need to check the bottle for 'made in Germany' to know your not getting an inferior product. At they end of the day they are all fine but M1 30w always shows higher iron in OUAs though we're talking very little overall wear here. It may be coincidental but in our motors, iron would most likely come from the valve train. Maybe its draining off before cold starts or it's something else but i didn't care for it. These motors tend to last for 200k if you change properly with just about anything. I just get (removed) sometomes.

[Kissfan79]

Understood. It just seems like there are a lot of negative opinions about Mobil 1 even though it is supposed to be a top motor oil to use. Have you ever tried Amsoil? Just out of curiosity.....where do you get your Schaeffers from and how much does it run you a quart if you don't mind me asking?Jim

[goodvibe]

I've got a distributor a couple miles from the house. http://www.nelsonmotorsports.com/synoilshp.php