Using to much petrol

[Ron41]

I would do about 90 % of Hwy driving but my car is guzzling the fuel, I worked it out to 13.7 L to 100 klm's, I am very gentle with the accelerator so I not using excessive petrol that way either.

I done a fault code check and nothing come up on that, can there be someone like oxy sensors that are rooted but don't come up when checking the fault codes ?
Tyres are all pressured up right, I can't smell any petrol leakage any were,spark leeds are good, spark plugs are good as well, but I did change the gap this morning back to the proper 1.5 mm [local mechanic had them down to 1.3 for lpg], would the smaller gap cause that much excessive petrol use ?
Air filter is clean and the maf sensor is clean, throttle body and IAC are clean.
About 2 months ago I had head gaskets replaced and valve grind done if that makes any difference.
Any help is appreciated.
thanks

 

[PlenumBiscuit]

13.7 litres :s pretty heavy

mines using about 10 litres for 100km, as i hope when i get 26 litres ($40) at the bowser its gonna get me through 260km for the week

im still upset with this, and very down about my VS petrol use

anyways i did a study and put together a few things that im trying to tick off here...
My Study

I recently bought a new Coolant temp sensor, hoping to gain correct readings to the ECU, and stop it running rich, but the sensors stuck in the block grrr

anyways as a fellow disgruntled vs driver hope this helps

 

[Ron41]

Thanks mate, I would real happy to get your fuel economy, mine is defiantly **** house, cheers for that study link mate, appreciate it.

I don't won't replace parts unless they are really nackered, would one of those scan tools the mechanics use show up any problems compared to paper clip way we check for fault codes ?

 

[James39]

I take it you have replaced the 02 sensors? Old means they are worn and because you are not seeing codes does not mean that they are working properly.

 

[Brett_jjj]

You should get someone on here to do a simple memcal tune, this will help considerably with fuel usage on these V6's.. I can get down around 6 - 7 litres /100 km on the highway , and I get anywhere from 9-12 around town, depending on the traffic etc. Ive just got a standard VS V6 exec, Its kept in perfect mechanical order, its only got pacemaker extractors and a cheapo sports type exhaust. Ive done a heap of experimenting with the memcal tunes on these V6's and I reckon Ive got mine about as good as it can get. I also use 98 octane fuels, you get less of it at the bowser, but I find I go further ,even though I get less of it for my money..The car just runs way better on the 98 fuels, and ive found that even with a standard tune fitted it still runs way better on 98.

Another thing Ive found that makes a pretty big difference is the wheel alignment-the caster angle. People seem to think that a wheel alignment makes stuff all difference to fuel usage, but I found that when I got the caster angle set dead even on both sides, the fuel usage noticably dropped again. The alignment guy had to loosen and adjust the K frame to get the caster absolutely dead equal both sides, but its was well worth the stuffing around with it,, the car drives way way better now.
It took me several alignment places before I found someone who actually knew what they were doing and talking about, the other palces I went to tried to say that the caster angle readings are puropsely set different to compensate for the road camber, which is just crap as my car still steers beautifully on high camber roads, having it set differently just makes the car use more fuel. The car is just so much better now Ive had it set like this, and I couldnt be more happy with the fuel economy Im now getting. Lastly, non genuine 02 sensors are rubbish and most dont work properly, causing the vehicle to use more fuel etc, only fit genuine sensors, theyre more expensive, but genuine sensors will save you more money in ther long run..

 

[Ron41]

Yeah mate, the Oxy sensors were changed about 5 years ago, they were not Bosch ones so if they don't throw a code when buggered, it seems likely they could be the culprit or part of the problem.

 

[Ron41]

Thanks Brett, I will order some new Bosch oxygen sensors, haven't had a front end alignment for about 3 years so I will get that done as well.
The memcal was done by Delco wizzard a few years back, so I'll see what happens.

thanks everyone for your help.

 

[Brett_jjj]

Delcos tune should be pretty good already, hes been doing them for years now... He was actually the person who helped me out and gave me a few pointers about tuning when I first started out a couple of years back..
New bosch 02 sensors should definitely help, they should generally be replaced every 80,000 to 100,000 km to keep the vehicle getting the best possible economy.
The fuel injectors are another item that can cause the engine to lose both power and economy over time as they get dirty and/or clogged up etc. These should probably be replaced every 4 or 5 years, it helps by using a quality brand fuel injector cleaner every 3 months or so, I use a whole bottle of cleaner (wynns etc) to a tankfull of fuel, and make sure I open up the throttle heaps so the injectors get a good workout whilst the cleaner is going through them. Using 98 octane fuels also helps keep the fuel system clean, and adding a cup of methylated spirits (metho) to half a tank of fuel every 6 to 12 months will help remove any moisture buildup in the fuel tank, and metho wont hurt the vehicle. The metho lets any moisture thats in the fuel tank, mix in with the fuel, so it can be consumed along with the fuel as its used. Water normally sits underneath the fuel on the bottom of the tank where it stays seperated from the fuel.

 

[Ron41]

Thanks Brett for all your good advise, I will do all the suggestions.

Have a great weekend.:thumbsup: