My 1984 Jetta Diesel (Normally Asthmatic, 5 speed - 7A transmission) gets about 46mpg in a mix of city and country driving (2 and 4 lane rural highways, a little Interstates highway driving, plus small town driving). On long, cross country trips, it varies depending on which way I'm going (and which way the winds blow). The best I've gotten from a tank was 54mpg (mostly I95 along the Florida and Georgia coast). The worst was I80 westbound across western Nebraska and Wyoming. I had to run 4th gear then against the 30-40mph headwinds, and I only got about 38mpg.
It's about 2,150 pounds with me and another passenger in it (typical for around town driving, 2,025 pounds with just me, close to 3,000 pounds for the cross country trips with 2 people, luggage, clothing and personal gear for both, plus camping gear, cooking gear and other assorted cargo). Mods are cowl induction fresh air intake, K&N filter, Autotech Tri-Y header, Injection pump adjustments (full load fuel increased, timing advanced until it starts getting loud with the cold start knob pulled [about 1.06mm]), stock 1 5/8" exhaust from the header back with stock resonator and muffler (changing that to 1 3/4" aluminum pipe straight to a Supertrapp), BMW 5.5x13" "alpina" style wheels (although I got the same basic results with 5x13" early Scirocco wheels), rear disc brakes (now aluminum calipers), and cheap, light weight 175/70-SR13 tires.
That's on conventional diesel. I'll have it going on the straight veggie oil conversion this week or next, and we'll see how it does on that.
My previous diesel, a 1980 Rabbit diesel, 1.5L, 4 speed (GC transmission) got about 45mpg in city/country driving, about 42mpg on long trips, and one time I ran a Porsche club drivers school in it at Roebling Road (Savannah, GA) and stomped it all the way down to 36mpg on the track. With the GC 4 speed, highway mileage suffered some because it turned a lot of revs at highway speeds (65-70mph). I ran it on 155R13 tires and 175/70R13 tires on the street and 185/60R13 DOT race compound tires the weekend on the track. It got slightly better mileage on the 155R13's than on the 175/70R13's. It handled much better on the 175/70R13's and stuck as good as any ITC rabbit on the 185/60R13 race tires.
For that track weekend, it also had the racing coilovers, springs and shocks installed from the ITC Rabbit I drove at the time. My co-driver rolled the race car and did some severe body damage to it one week beffore the Porsche Club school, so I put the race car suspension on the diesel and ran the school in that. My main purpose at the school was to learn the track (I'd never raced there before that time) and the diesel did provide some interesting feedback about your driving line. If you slip the thing off line, it scrubs off speed that you don't get back for a long time.
Topic: IDI engines: fuel economy comparison (Read 32298 times)
