That's probably reasonable. The speedo may be reading low because of friction due to wear and tear since 1982; you could have the speedo overhauled and it might help, might not. A speedo can be recalibrated for a change in transmission or rear end gearing or different size tires by introducing a little gear thing in the speedo cable. Auto repair places usually have access to such things.

Also, just because the speedo is low doesn't mean the odometer is also low, so don't go bragging on your mpg yet.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970