Engine Oil Number Help

If you don't have engine no-start issues, then don't worry. Since the ambient temp is warm in your location, I don't think you'll have any problems other than slightly worsened fuel economy.

Try to use 5W-30 for your next engine oil change if you can find another place to change your oil, or if you can do the work yourself.

 

To explain it simply (over simply, but just for the concept):

For a oil viscosity grade like 5W-30, the 5W refers to the cold oil viscosity (cold as in when the engine is cold) and 30 refers to the hot viscosity (hot as in when the engine is at normal operating temp). Viscosity is the thickness of the oil.

So the 5W-40 is ok when the engine is cold, but it is thicker than Toyota recommends when the engine is hot. The thicker oil may reduce mileage because it takes more energy to move it around and creates slightly more drag on internal components. It is probably more appropriate to use 40 weight if you are driving in sustained high temps above 100°F (38°C +)(like in the desert during summer).

 

?? The explanation is completely correct but the conclusion is wrong: his engine will be hot almost all the time, therefore given a choice between 5W-40 and 10W-30 he should use the oil which has the correct *hi temperature* weight, namely the 10W-30.

 

Yes, its true that the engine normally spends the majority of the time in the "hot" range. I don't think it will damage anything to run the 5W-40, it might lower the FE as Patrick stated earlier.