I bring my 98 4-cyl Accord to Honda dealer for regular oil change.
Lately, they started use 5-20 oil for oil changes for all the cars.
The advisor told me that unless I explicitly tell them otherwise, they
will be using 5-20 oil as default.
My question is: Since my car is not new(7 years, 105K miles),
can I still use 5-20 engine oil? Will it offer less protection than
5-30 or 10-40? After all, 5-20 oil is newer and more expensive.
Some people tell me to switch to 10-40 oil as car ages. When should
I be switching to that grade?
Thanks for your help in advance.
I would just go with what the dealer recommends. that's usually the best
thing. i'm wondering about that weight of oil myself because i have a real
old civic that calls for 5w-30 and i wonder if it would be better with
Here is what I learned about the chemistry of motor oil about 8 years
ago (I needed the information for a technical paper). The information
may be out of date, but I would think it still applies.
So called multiviscosity oil (a misnomer) contains hydrocarbon
polymers. Polymers are molecules built around long chains of carbon
atoms, maybe 100 or so atoms in the chain. Plastics are polymers. DNA
is a polymer. Polymer just means a long chain of similar units.
These long molecules are tightly coiled up at low temperature (due to
hydrogen bonds) but at higher temperatures, the molecules uncoil and
get tangled together. This "tangling" effectively gives the oil a
higher viscosity and is what causes the viscosity of the oil to remain
higher as the temperature is increasaed.
The problem is, as I understand it, that for oils with a wide
difference between low and high temperature viscosity (such as 10W-40)
such a large quantity of polymer must be added that the polymers
begins to gunk things up. So it is best to stay with an oil where the
two numbers are closer together.
My Honda owners manual recommends 5W-30, but allows 10W-30 in certain
temperature ranges. Down here in Texas (where the temperature right
now is 81 degrees) it never gets cold enough to neede the lower
viscosity oil, so I always insist on 10W-30. The polymer problem MAY
be why Honda and other manufacturers have gone to 5W-20 as a
On the other hand, there are many characteristics of motor oil that
are a lot more important than actual viscosity. As another poster has
said, these include such things as film strength, ability to hold
contaminants in suspension, etc. Modern motor oils are far superior
to the stuff I had to pour in my car 50 years ago and are an important
part of the reason why automobile engines can easily go 200,000 miles
or more with no problems.
Just my $0.02 worth.
Freelance Science Writer and Editor
I would use whatever grade your original manual calls for, which is
probably either 5W-30 or 10W-30. I am not aware of Honda recommending
the application of 5W-20 to vehicles which did not originally specify it.
10W-40 was common in older cars, which tended to become oil-burners with
age. It doesn't flow as freely as 5W-30 so it doesn't lubricate quite as
well. All things being equal, all viscosities would be fine. It is the film
strength, not the viscosity, that provides the wear protection. But low
viscosity helps the oil actually get to where the lubrication is needed, so
in the real world of modern engines it lubricates better. I agree with the
others, though; if Honda felt 5W-20 was the right choice they would have
Changing to 10W-40 in a Honda is an end-of-life move; an acknowledgement
that something has already gone wrong (like an inadequate air filter being
used for too long, or too infrequent oil changes) and the engine is being
nursed along another year or two. Improvements in engine production have
ended the oil consumption problem in most engines.
for the right price i would use the more advanced motor oil 5w-20. more than
likely it is a better oil for your car. your owners manual was written
before that oil was even thought of probably and now it's out and if your
manual could be rewritten it may actually be calling for w20. i wouldn't
worry about it. if the car is running good and you talk to the dealer and
they tell you its a better oil. than you can use it.
Certainly I would use the latest SM / GF-4 rated oils, but oil quality
and oil weight are two different things.
Ford went to considerable trouble to publish service bulletins showing
which older models were demonstrated to be compatible with 5W-20 after
Ford switched most of their new vehicles to 5W-20. However, I have
never seen any similar publication from Honda, which makes one wonder if
there are issues with using 5W-20 in Hondas which did not specify it
By the way, Ford stated that the primary reason for using 5W-20 is for
improved fuel economy over 5W-30 and bragged about the expected 0.6%
improvement. Somehow I don't think any of us would ever be able to
detect a less than 1% fuel economy improvement.
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