Hey Ken, this one’s for you, hope you can put your two cents worth in.
For years now I’ve been using Mystik (Citgo) JT-7 80W-140 Multi-Purpose Gear Lubricant which I get from the Farm & Fleet stores around here. Since I just finished up rebuilding the SM420 in my ‘50 this week I thought I’d go with a synthetic oil, after all 50,000 racers can‘t be wrong. So I just topped off the trans with a quart and a half of Mobil ‘1’ 75W-140 LS Synthetic Gear Lubricant. It says Light Truck & SUV Formula on the jug. Since the old gal has been put out to pasture and isn’t going to do any heavy hauling any more, unless one considers my “big old wife” as heavy hauling, I figure she falls into the light truck category. The Mobil ‘1’ seems quite a bit thinner than the Mystik but both of the gear lubricants meet API GL-5 quality so does anyone see any problem with using the Mobil ‘1’ synthetic, other than it costs four times as much????
Denny Graham
Sandwich, IL
