My WB used to get about 18m/g. It was standard with quadrajet and electronic ignition, 3:36 diff. I didn’t drive for economy though.

I didn’t see the part where they got 22pmg, I would have to drive slower and keep the engine revs lower in order to achieve that.

Yes everything is correct for the engine as nothing has been changed since it sat in the shed for 20 years and I have just been refurbing all existing parts, in regards to the carby, it is for a manual 253 and not auto, I made sure of this when getting the carby rebuilt. Yes I am pretty sure it is the 3.08 banjo as auto got the 2.78 in the 253 and the 350 got 3.36 and I don’t have LSD. It even has factory twin exhaust system. option.

The car does smell a bit ‘fuely’ but I put that down to it being a carby engine and not fuel injected.

I was probably going too fast and giving it stick, but is there an optimal mph/rev to sit on? E.g 60mph returns better fuel economy than 70mph?

Like I said I didn’t buy it for fuel economy, but wanted to make sure I didn’t have a problem with excessive fuel consumption, as that’s not fun over fuelling the engine. So wanted to hear from other 253/308 owners who have a similar factory set up to me

I am hoping to catch up with a mate who has an identical car and set-up and compare the 2, but dont know how we will do that without going for a long trip.

Edited by user Tuesday, 16 October 2018 10:03:02 AM(UTC)  | Reason: Not specified

Yes, have checked all of that and nothing obvious that can been seen e.g stain marks.

I thought the formula to work out mpg was, miles divided by gallons = mpg

e.g 231 miles divided by 14 gallons = 16.5mpg

Yeah that's the formula, but on your way up (to use your example) you did 231 miles for 53 litres. That's actually 11.7 gallons in Australia.


So 19.7 mpg.

In US gallons you'd get the figure you worked out, but I believe the figures others have quoted from Motoring magazines would be in Aussie gallons which is what you need to compare it to.

I'd be happy with close to 20mpg. You might get a bit more by better tuning (like optimise dizzy advance and carby jetting) for ULP. A HEI dizzy and coil might improve it a tiny bit too if graphed right.

Funny the perceptions of economy today, people always tell me my Hilux uses too much fuel (despite them never owning one), and buy a diesel instead and pay more for it. In reality in standard form the Hilux would be similar to a 202 HT-HQ, even better at cruise (like straight roads at 100km/h), the only times you'd see worse than 14-15L/100 would be towing. But even 10-15 years ago you couldn't give away a 6cyl HK-HQ, everyone wanted the bigger, more powerful, stronger drivetrain V8 versions. And today people would rarely take a 6cyl SL/R or GTS or Sandman over a V8 one even though the 6cyl ones are collectable today. 20mpg used to be reasonable economy, from a 1.3 tonne car. Today you get 2tonne V6 Hiluxes and 2.5tonne V8 Landcruisers that do that easily and they are shunned!

GMH used to promote the 253 as a V8 with 6cyl economy. And I guess the fact that in a Holden most 6cyl were 3.55 rear axle whereas the 3.08 (which was developed for the 253) rear axle would have been a large part of that.

I think 80km/h used to be considered an optimal speed to sit on for fuel efficiency, but buggered if you'd find me cruising at that speed on the open highway just to save a few bucks!!

I thought that in Australia the Super petrol was 97 octane to the end.
There was a low lead I remember in the years near the end of Super in QLD I used it once but I did not think that the octane was lower than 97.

We just had 91 and 92 octane unleaded from 1986 I do not remember if 95 came out in 1986 as my first unleaded car was in 1992, I know they had 95 then, but how many unleaded cars needed 95 before then, as we still had 97 leaded then I am sure.
Around 1994 I think was the end of lead fuel and you had to use 95 octane with flashlub, I never had to use that stuff. but my wife's dad had a dizzy graph machine that he would reset the timing advance back a bit down low rpm mainly and see how it went from there so they could run on 95 octane without pinging. one I seen him do was a 1968 Galaxie with a 390 V8 9.5:1 I think they had, so she needed to be done. one could just retard the whole thing by timing light but I think it better to re graph.

If a car was to run on 97 Super and you go put 95 in it, all could be fine unless your compression ratio is high needing 97 but most should of been ok on 95 but people wanter to use 91-2 unleaded in there cars that used Super and that's when they ran into problems, Standard was 89 octane and if you went over say 8.3:1 I think it was with iron heads you were looking for Super unless you retard the timing a bit.
So running 91-2 octane would be 8.5:1 fine to about 8.7:1 at the max I would think.

When 98 came out there was some playing about with the fuels Shell, had one that could cause a bit of a problem with jetting bikes mainly, you had to lean it out a bit to get the best out of such and all was fine, but some bikes were better to go to BP etc for 98. but most bikes were fine on 95 octane, my dirt has 13:1 and 95 is recommended and fine, and I mainly run it on 98 and have ran 98 E10 and then it smelt different and ran a little leaner, power wise I don't think it lost any as it's a little on the rich side, so I think if anything picked up a bit more power maybe.

The First of the E10 when it first came out was crap but it got real good when Shell brought out a new improved economy type they called it and nothing but good results with E10 nowadays, I would not use anything other as power improvements can be great but there is a E10 91 octane out there at some BP that is not as good as the E10 94, I would say that any car from 2010 running on E10 94 will perform real well over the 91 unleaded crap.
But for Boats I would use unleaded.

My wife's Toyota Aurion goes like the clappers on E10 94 it's truly amazing the difference as the 91 unleaded is crap, the manufactures all are suppose to be running on 95 octane but they sell then as 91 ok, but what that does is the computer has to retard the timing back to run that crap and you loose power and economy.

NSW has been running only E10 now I think.

A mate was using the dregs off his distillery and poring it into his bike and all was fine, Honda CR500 it was, so mixing oil as well in a 2 stroke.
He drank 500ml of rum a day then and still does plus beer that he makes as well.
So he made a fair bit of dregs in what he was distilling.
He wanted me to buy a setup, and said it would pay off in 3 months, more like 3 years or more for me I would think, but he believes everyone drinks like him, I said no mick I do not drink on week days, he believes I am joking.

I have pulled off heads that had been done up with only 3weeks driving and the carbon looked like it had don 100,000miles on leaded fuel.

I remember a due that was complaining about getting a full recon engine and It blew up after 3 months or so and he took of the head and went off his rocker claiming that it was an old engine that had just been painted, but no it was a fully reconed.