The number in the viscosity that you really need to be concerned with
is the first number. This is the base weight of the oil. Conventional
multiviscosity oils start with 10 weight oil for 10w30 and add chemicals
that make it behave like 30 weight when it's hot. The fact that these
chemicals are burned off contributes to the need to change the oil at
regular intervals. (another good reason is that sulfuric acid forms in
the oil due to sulpher in the crude oil from which conventional oil comes)
Synthetic oils can have a very wide range of viscosity rating (5w50)
since they consist of a totally manufactured molecule. They can be engineered
to flow like 5 weight while maintaining the viscosity of 50 weight
when hot. If you are running 10w30 synthetic, I don't think that 5w50
is going to help increase your oil pressure, but 20w50 might. I ran
10w30 synthetic (Mobil 1) last winter, and switched to 10w30 conventional
(Castrol GTX) in the spring. The GTX gave me a higher reading on the
oil pressure gauge than the synthetic despite the warmer temperatures.
I personally wouldn't worry about the lower reading when using synthetic
oil as long as it stays above the lower end of the marked range of the
gauge. You might try a change with conventional oil if you are worried
about the condition of the motor.
My $.02. YMMV.
-Jim.
'87 v6 auto 4x4
> Now, for a question for everyone. In the dakota owners manual, they
> recommend using only 10w-30 oil and suggest not using any heavy
> weights. I run synthetic oil and have been considering running 5w-50 or
> 20w-50 to increase my oil pressure. Anyone else running higher
> viscosity oils? My oil pressure seems a bit lower than normal, about 1/8
> to 1/4 on the gauge, I have been told synthetic oils tend to have lower
> pressure because they flow better; higher velocity thus lower pressure.
> I have a 91 dakota with a V-8 with 76,000 miles its always had synthetic
> oil so I wouldn't think it is worn out. Any opinions?
>
> Brent
> 91 V-8 4x4
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