I know it has been asked TOO MANY times, but what what viscosity would be best in an extremely hot climate? Everything I have found while searching pointed to colder climates so I didn't know if it was relevant to my situation. I currently have a H23 that is waiting to be swapped for a H22A so I recently bought a large amount of 5W30 oil that was being liquidated at work. I always assumed the H22 liked a thinner oil compared to my H23 which had always seen 10W30. I know the basic idea behind 5W30 is better for cold temps and 10W30 for warmer, but my owners manual said I could use either 10W or 5W in the H23. I was curious so I decide to look up the viscosity chart in my helms and to my surprise it states that I am WAY out of the temperature range for the H22A1. It recommends 5W30 for 30F and below and 10W30 for 0F+. Living in southern Louisiana where the ambient temperatures are always high (88F today for example), that information kinda scared me. So basically what I am asking is that in this climate would 5W30 be safe for a H22A? I do plan on running the engine hard and doing a lot of stop and go driving/sitting in traffic. Should I return all the 5W30 and grab up all the remaining 10W30?

 

If you keep to good oils like Mobil, Amsoil, Torco...etc then i wouldn't be necessarily concerned. some of the conventional oils have the tendency to breakdown easily and essentially lose all the viscosity and turn into what might as well be water. I'm in florida and have used 0w, 5w, and 10w without any problems. The oil cap says to use 5w30 and that is what i have typically ran in the motor.

look up some posts by "Master of the Universe". He has done a lot of analysis on engine oils and has contributed a number of very informed posts about engine oil.

 

Well it is conventional Formula Shell oil...

 

You really need to look at the specs rather than just assuming 10w30 is thicker (or better) for warmer climates. In the Mobil 1 lineup, 5w30 is superior than 10w30. It has a higher flash point (230*C vs 224*C), higher viscosity index (169 vs 147) and higher viscosity cSt@100*C (11.3 vs 10.0).

For my application, my next fill will be M1 0w40... the specs are comparable to Redline 5w/40 but costs less. I want/need better protection from a thicker oil for my supercharged motor. But if I was NA and drove a street only commuter car, I'd run 5w30 year-round.

 

the 5w and 10w have to do with cold starts.

"Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils."

5w30 and 10w30 have the same viscosity at engine operating temperature.