said by Reg Mauler :

Ok so here's the deal, we just got a new car (2007 Honda Accord SE 4 cyl) about a month ago and we are moving down to Phoenix in about a week. I want to change the oil before we go so I don't have to mess with it down there (just one less thing to worry about). My question is, the engine calls for 5w-20 but down there it is very hot so I was thinking of putting 5w-30 in it (synthetic of course). Will this be acceptable? I would usually just go with my gut on this sort of stuff as I'm usually pretty knowledgeable with things like this but I figured I would ask some of the people in here who may have more experience then me.

said by WTF :

Consult your owner's manual, and use what it tells you to, based upon your climate. A 5W-20 will provide faster flow and superior lubrication (as in less time to achieve oil pressure) in cold weather. Also, the narrower weight gap (5W-20, as opposed to 5W-30) means that the oil is more stable in maintaining it's specified viscosity.

However, any oil's performance is optimized to a certain operating temperature range. A 5W-30 weight engine oil will be much better suited to higher temps, as in spring to summer weather conditions, whereas a 5W-20 oil is not designed to operate in those higher temps, and will break down and start to oxidize fairly quickly ( with the possible exception of a high-quality FULL synthetic oil). The reason for using a 5W-20 or 5W-30 in newer cars (as opposed to a 10W-30 is because in new engines, the critical internal clearances are much tighter (sometimes as tight as 2 to 5 ten-thousandths of an inch, or .0002-.0005).

The lighter viscosity oil will provide lubrication much quicker, and reduce contact wear considerably better than a 10W-30 oil. Overall, probably the best bet is to use a 5W-30 oil most of the time, because it is a wide range protection oil, and swith to the 5W-20 in much colder climates. As the engine accumulates mileage, you can think about switching to a 10W-30 to compensate for larger internal critical clearances due to normal operational wear, but know that increasing viscosity increases the time it take to achieve full oil pressure, thereby increasing initial start-up wear on all sleeve, non-roller bearings, and pushrod/rockers/cam lobes.

Sorry for being long-winded, but I hope this helps!

said by Reg Mauler :

So basically the debate comes down too 20 weight vs 30 weight.

said by mattmag :

Actually there should be no debate at all.

Follow the instructions in your owner's manual for the proper weight oil to use. There is much mis-information circulating about motor oil and what the viscosity specification truly means, and some of it has found its way into this thread.

Bottom line= do what the manufacturer says to do for your particular situation. You'll never go wrong.

-Matt

said by mattmag :

Actually there should be no debate at all.

Follow the instructions in your owner's manual for the proper weight oil to use. There is much mis-information circulating about motor oil and what the viscosity specification truly means, and some of it has found its way into this thread.

Bottom line= do what the manufacturer says to do for your particular situation. You'll never go wrong.

-Matt

said by 3SGTE :

Have you looked in the manual?

Some of them have temperature dependant ranges that result in the vehicle having two specified acceptable viscosities.

What does the manual actually say?