Recently I put 5oz of Amsoil 100:1 Pre-Mix oil into a full tank of gas in my 1997 Expy, 5.4 with 108,000 miles. I noticed (or I think I noticed) that it ran smoother and had better throttle response. The gas mileage stayed the same. I can see where this would lubricate injectors but is it also lubricating valves like Lead substitute does in my 56 ******. The lead substitute in the ****** makes the engine quieter and run smoother. Is this 100:1 doing the same thing in my Expy or is it just my imagination?

 

Well the most likely explanation would be that the addative changed the octane rating (and hence rate and other properties of combustion). The engine may have been gradually running less than optimal and this sudden change in fuel made comparison noticable, Simply try a higher octane fuel and see if the change feels the same. It's unlikely you have removed enough friction that you would feel the difference.

 

Flagracer, you must be right. I've since run a tank of 92 octane without ethynol and it seemed crisper,smoother like when I had the 100:1 in the gas. When I run 87 octane it is noticeably less responsive. Thanks for the reply.

 

Glad it worked out for you