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JohnAh · 03-24-2015, 02:47 PM

I drive a 1975 Saab 96 V4 and they can easily consume over 8 litres per 100 km (35 mpg) while following the traffic average on highway mixed with city driving. My consumption made a steady drop to 7 L/100km (40 mpg) when I decided to set 80 km/h as my personal speed limit. Wind resistance is at least a square function, or is it even a cubic relation?

Next big saving was to stop using the brake all the time. Instead I carefully study surrounding traffic and use just the right ammount of throttle combined with a lot of coasting. This got med down to about 6 L/100km (47 mpg) so it's actually even more rewarding than just reducing the top speed.

The old Saab has a Ford V4 carburetted engine and I mix about 25-30% ethanol to the petrol. This LOWERS the consumption sligthly and reduces detonation and "glow-ignition" (guess there's a better word I don't know about in english) This is important for the final change in driving style and the only physical modification I have done.

By installing a kill-switch on the gear lever, next to a start-switch, I often manage to keep fuel consumption around 5 L/100 km. The gear lever is located on the steering column and the gear box also have a freewheel so it's very easy to start and stop the engine frequently. I practise "Burn & Glide" a lot and it's amazing how far a car can travel without the engine running. As a side benefit of this driving technique I'm also superior to planning my driving compared to other drivers. -It's not usual that I sooner or later manage to pass the same cars over and over again despite my slow driving. I guess this driving style has also made me a much safer driver.

5L/100km = 56 mpg and that's a realy good average for a 40 year old "scrapmobile". My best from last summer was a vacation trip overseas to Finland (I live in Sweden) where I got 4.8 L100 with wife, three children and lugguage. (=59 mpg)

The trick is to keep the engine in the BSFC sweetspot while working and if it can't be kept there it should be switched off until next time it's needed. The throttle isn't actually bad, it only converts the expensive fuel to the travel wanted. Using the brakes is wasting all that energy to heat and a proof of poor planning.

Low weight is only beneficial in city traffic where it's more difficult to plan driving without brakes. A higher weight can actually improve fuel efficiency outside city traffic by smoothing out the continous changes in speed while practising Burn & Glide.

03-24-2015, 02:47 PM	#45 (permalink)
JohnAh EcoModding Apprentice Join Date: May 2012 Location: Vallentuna, Sweden Posts: 129 Phantom Blot (Spökplumpen in swedish) - '75 Saab 96 V4 90 day: 52.77 mpg (US) Thanks: 17 Thanked 55 Times in 30 Posts	I drive a 1975 Saab 96 V4 and they can easily consume over 8 litres per 100 km (35 mpg) while following the traffic average on highway mixed with city driving. My consumption made a steady drop to 7 L/100km (40 mpg) when I decided to set 80 km/h as my personal speed limit. Wind resistance is at least a square function, or is it even a cubic relation? Next big saving was to stop using the brake all the time. Instead I carefully study surrounding traffic and use just the right ammount of throttle combined with a lot of coasting. This got med down to about 6 L/100km (47 mpg) so it's actually even more rewarding than just reducing the top speed. The old Saab has a Ford V4 carburetted engine and I mix about 25-30% ethanol to the petrol. This LOWERS the consumption sligthly and reduces detonation and "glow-ignition" (guess there's a better word I don't know about in english) This is important for the final change in driving style and the only physical modification I have done. By installing a kill-switch on the gear lever, next to a start-switch, I often manage to keep fuel consumption around 5 L/100 km. The gear lever is located on the steering column and the gear box also have a freewheel so it's very easy to start and stop the engine frequently. I practise "Burn & Glide" a lot and it's amazing how far a car can travel without the engine running. As a side benefit of this driving technique I'm also superior to planning my driving compared to other drivers. -It's not usual that I sooner or later manage to pass the same cars over and over again despite my slow driving. I guess this driving style has also made me a much safer driver. 5L/100km = 56 mpg and that's a realy good average for a 40 year old "scrapmobile". My best from last summer was a vacation trip overseas to Finland (I live in Sweden) where I got 4.8 L100 with wife, three children and lugguage. (=59 mpg) The trick is to keep the engine in the BSFC sweetspot while working and if it can't be kept there it should be switched off until next time it's needed. The throttle isn't actually bad, it only converts the expensive fuel to the travel wanted. Using the brakes is wasting all that energy to heat and a proof of poor planning. Low weight is only beneficial in city traffic where it's more difficult to plan driving without brakes. A higher weight can actually improve fuel efficiency outside city traffic by smoothing out the continous changes in speed while practising Burn & Glide.