On a 1,700 mile trip thought I'd check out the speedo & odo since there's not much else to do on I95 for 400+ miles. The odo checked out fine on a couple of 50 mile comparisons - 0.7% off; not bad. But the speedo, at an indicated 55 mph was a true 60 mph, per the mile markers & my watch. At 60 indicated, a true 65; at 65 indicated at true 70, etc. Since I don't have a tach in my '80 242DL I'd like to know the approx. RPM & I would know that if I could trust the speedo. Don't think I have a cable problem since the odo is OK. Do these units need lube or something after 29 yrs., but only 41K miles? The needle flickers a little sometime but that's the only problem I thought I had until I did all this checking. There is an outfit in Austin, TX that will overhaul & recalibrate the unit for $75. Do you think I really need it? Thanks.

Cal