Gas mileage drops?

1995 Toyota Tercel, 1500cc, 212,000 miles.
Took 1500 mile round trip. Cruise control set to 60-61 mph. Get 500 or so feet behind trucks in the slow lane and don't use pedals for 2-3 hours at a time. Comfortable no stress way to drive. Interstate 5, CA and OR.
First two legs = 43+ mph. (the usual). Last 3 legs = 38.6 mph.
What could have gone wrong? Car seems to run fine. (City mileage has always averaged 33-34 mpg.)
BTW own an identical parts car (rear ended). Cheap at $200. Low (132K) mileage.
All suggestions appreciated.
Ivan Vegvary

Ivan Vegvary wrote:
> 1995 Toyota Tercel, 1500cc, 212,000 miles. Took 1500 mile round trip.
> Cruise control set to 60-61 mph. Get 500 or so feet behind trucks in
> the slow lane and don't use pedals for 2-3 hours at a time.
> Comfortable no stress way to drive. Interstate 5, CA and OR. First
> two legs = 43+ mph. (the usual). Last 3 legs = 38.6 mph. What could
> have gone wrong? Car seems to run fine. (City mileage has always
> averaged 33-34 mpg.) BTW own an identical parts car (rear ended).
> Cheap at $200. Low (132K) mileage. All suggestions appreciated. Ivan
> Vegvary


Different fuel blends?

--
Steve W.

Thanks Steve,
Possible (fuel blends) but last leg was Oregon gas just like the first two.
Thanks! I
Ivan Vegvary

"Ivan Vegvary" wrote

> 1995 Toyota Tercel, 1500cc, 212,000 miles.
> Took 1500 mile round trip. Cruise control set to 60-61 mph. Get 500 or so feet
> behind trucks in the slow lane and don't use pedals for 2-3 hours at a time.
> Comfortable no stress way to drive. Interstate 5, CA and OR.
> First two legs = 43+ mph. (the usual). Last 3 legs = 38.6 mph.
> What could have gone wrong? Car seems to run fine. (City mileage has always
> averaged 33-34 mpg.)

Was the entire trip on a perfectly flat road in a vacuum?
You can't compare "legs" unless they are exactly alike.
Hills (even barely noticeable ones) take more gas to climb. 750 miles downhill
(going out) will use less gas than 750 miles uphill (coming back), even though
it still comes to a total of 1500 miles "round trip".
Headwinds take more gas to fight than tailwinds.
Road surfaces can produce more or less drag depending on material used.
Drafting other vehicles helps, but only at certain speeds & distances.
Way too many variables to decide if something has "gone wrong".

Thanks, Sanity Claus,
No, things are never equal. Left at elevation 1000, climbed over the Sysique Mts. (Almost exactly halfway). Ended up in SF Bay Area elev. 25.
I suppose there were headwinds on the way back, which means there were probably tailwinds on the first legs.
Thanks for the good hint.
Ivan Vegvary