Lubemaster, what do you think ??
 

I changed the oil in my Exploder from a straight Valvoline dino to the same weight 5-W30 Castrol Syn blend. I immediately noticed a 2-3 mpg improvement in fuel economy. Was it the oil ??? Is it the warmer weather ??? What do you guys think ??

Your wallet is lighter by several pounds. Less weight, feel better. Mileage goes up.

Increased fuel eco is the first thing many folks notice when going to a blend or straight synthetic - this is real noticable with older engines. There are a few reasons why; increased lubricity, stable viscosity means better film formation, many blends and straight synthetica actually help remove deposits that have formed. This is especially true of the esters and to some extent the PAO's.

Better milage can also be achieved when you switch to a lower viscosity oil - say a 10W30 as opposed to a 15W40. Be carefull with that though because some engines get kinda rattled when you introduce a thinner oil to the frey - it may reduce resistane but it can also mess up the main bearing lubrication resulting in increased wear .

Thanks Mike.

The engine has 65,000 trouble free miles on it so far and this is it's first taste of a syn blend. You mention that the syn blend may have loudened some deposits. Does this mean it should be flushed ?? How to do safely.
I change the oil and filter every 5,000. Oil analysis showed that I can probably increase the interval, but I have chosen not to.

Being an engineer, I am pretty anal about tracking the fuel economy and believe the jump to be accurate and not a figment of my imagination. Is this mpg increase temp or perm if I stay with the Syn blend ??

The deposits should/will be held in suspension through the dispersion characteristics of the oil package. I can send you some flushing oil that you can add directly to the crankcase a few days before you are to change the oil. It is the only product that will not adversely affect your oils properties and if any residual is left over it will not hurt. PM me your shipping address and I will get you some.

The increase in milage should remain.