[lyd]

Since I am paying close attention to speed, RPM and vacuum level, I noticed something disturbing in the last couple days.

I seem to have lost about 10 average MPH when maintaining the vac gauge at 10. I don't know if I am making less power in the engine, or if it is getting sapped away by one form of drag or another, but I can definitely see the change in speed at that throttle position as compared to a couple days earlier.

I can only identify 3 things that have changed about the time this started:

1. I got the new wheels and tires, same size as before.
2. It got significantly cooler out.
3. It has been somewhat more windy.

1 is possibility, I guess, if I have increased my rolling resistance -- but 10 MPH worth? That would be depressing. The old tires were not significantly worn, just dryrotted, so it is not like I was running tread-less before.

2 seems like it should create *more* power, with an accompanying drop in efficiency, all else being equal, but maybe I am thinking of that wrong.

3 is a good bet, but I am noticing the power loss pretty consistently regardless of the direction I am traveling.

Of course, there is a 4, and that is "something else happened to break/degrade/go wrong about the time of these other changes", and I'm not sure what to look for there. Engine runs fine and vacuum is still 19 or 20 at idle.

It is bugging me because when attempting to drive with load I am now cresting gentle rolling hills at 40mph or below on 55mph roads, which starts to get a little risky, imo.

Any thoughts?