Ask Sarah: Is my lube still good?

Oil is fairly cheap- at least cheaper than a new engine!  Newer engines have a lot higher standards than older engines.  They must last longer, be more fuel efficient, and pollute less.  To operate for a varied range of conditions, the engines use multi-weight detergent motor oils that contain additives.  Think about everything you’re asking your motor oil to do- minimize wear from metal to metal contact, transfer heat, and wash away all the crap (contaminants) that is a by-product of combustion. The oil must do all of this under a lot of heat and pressure, so if in doubt, throw it out!

Motul 300V Competition 15w50 is for cars that kick ass.  It's a high performance, racing motor oil intended for use in high-revving, naturally aspirated or forced induction engines.  Its double ester technology results in 0% shear loss, meaning none of its viscosity is lost during operation.  There are six viscosities in the 300V lineup that can be interchanged for different types of racing or longevities, ambient temperatures, or engine fuel dilution.

Generally, a more simple oil formulation will last longer.  Multi-grade oils provide better protection for a larger range of operating temperatures but a bigger difference between the cold and hot viscosities (such as your 5w30 oil versus 10w30) means there are more chemical compounds (viscosity modifiers) that can break apart.  With excessive heat, they could leave more carbon deposits on the valves.