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rwyatt80
09-09-2009, 11:47 PM
Hello,
Ihave a 96 accord lx 2.2l engine with 247,000 miles on it
and its time for an oil change. I currently use castrol hm gtx 20w50 but have been told that the weight is too heavy for my vehicle. Someone recommended castrol gtx 10w30 because of where I live (sc) and the way I drive (stop and go traffic, i also go out of town at least once a month).

What do you think??

All help is appreciated!!:-D

batever
09-12-2009, 01:10 AM
go with 5w-30 or 10w-40 or 5w-40.


personally I use 5w-30

understand that in these multigrade designations the 30 or 40 relates to viscosity at operating temperature (around 200F) , and the "5w" refers to viscosity at, I believe, 32F. The numbers themselves are related to viscosity numbers but are not viscosity (the ability of a fluid to flow under a given pressure and at a given temperature) specifications themselves. In other words, a 5w-30 oil does not have viscosity of either 5 or 30, the 30 and 40 are just figures that are relate to actual viscosity measurements. The 30 will flow easier than the 40.

however, a 5w at startup temperature does not flow as easily as a 30 or 40 at operating temperature. In other words, all oils are too thick for your engine at startup temperature, no matter how low that first figure in the specification.


Still, it's good to have as low a viscosity as possible at startup temps so 5w will be better than 10w according to this calculus.


Even a 5w-30 oil is way to thick at starting temperature to flow easily through the engine. On the other hand, it flowes better at startup than 10w-30. On the flip side, the 5w-30 has less resistance to viscosity drop (see later) than the 10w-30. But I think the startup viscosity is more important for the kind of driving you describe than the resistance to viscosity drop under heavy load./high temperature.

And when the operating temperature of 200F is reached, then the 30 grade oil is generally at a good viscosity for the car.

Some people prefer a 40 weight oil in the summer, 30 weight in the winter, but I run 30 weight (5w-30 multigrade) the full year round. I live in Massachusetts.

There are also straight grade oils (they will just be 30, 40 , 50 or whatever) but generally these are not used so much in commuter type cars but more in commercial vehicles or race vehicles. This is because they tend to be really thick at startup (where a lot of engine wear occurs) and not have good flow at startup, but maintain their viscosity better at high operating temperatures/once heated up than a multigrade oil. Multigrade oils (i believe this is the explanation) rely on a lighter weight base oil (this would be the 5 in the 5w-30) , then rely on different chemicals and polymers in the oil to keep enough viscosity at high temperature (the 30 in the 5w-30) to protect the engine. But because of their reliance on these additives and polymer components, under severe thermal load they can have temporary "viscosity drop" which you don't really want under heavy use. And in a commercial vehicle that only is started like once a day the startup wear is not significant. And in a race vehicle that is only run--who knows, a couple times a week-- it is not important. What's important is keeping the thing running during the race. And they replace or rebuild their engines on a regular basis.

I say go with 5w 30 but if that's too much of a switch for you go with the 10w-40. There really isn't that much of a difference. But definitely stop using the 20w-50 stuff.

rwyatt80
09-12-2009, 02:12 PM
I dont have a problem switching to what the manufacturer recommends, I just wanted some advice as I want my baby to go the distance. I will go with a high mileage 5w30. I will let you know what happens :-D

thank you!!

rwyatt80
09-13-2009, 10:01 PM
I have switched to 5w30. So far so good.Will keep you posted on any changes. Thanks for the info!! :-D

batever
09-18-2009, 06:09 PM
I have switched to 5w30. So far so good.Will keep you posted on any changes. Thanks for the info!! :-D

No problem. It should work out fine. The manual specifies either 5w-30 or 10w-40 based upon the air temperature so 5w 30 is a pretty appropriate choice.


Happy driving!

--batever