Fuel Consumption & Fuel System

[Simon Hornby]

Hi, I have recently bought a 1993 GS300 which I have to admit has grown on me. But I have to ask about reasonable fuel consumption. I have just filled up having done 282 miles it took 65 litres. This works out at about 21mpg. According to the Yahoo revue of the GS300 it should do about 26 and they a bloke flogging his on eBay at the moment claiming to be able to get 32 out of his. What is the real situation?

Now the car is due for a service so I would expect things to improve a bit after it's done. But there may be another clue to this poor performance...

When I open the tank to fill up there is the sound of rushing air from the filler cap. Is there a vent tube in the tank which could be blocked? Could this have a bearing on the fuel consumption? Any Ideas....

Does anyone know of any good Lexus technical web-sites?

Simon

[Guest inicol63]

I have to say that i was reading a manual on the LS400 and could not beleive that the GS300 was on par with fuel rating of the LS400

Even though the LS400 is v8 and the GS a v6.

Also the car you have maybe is a few years old, so you will not get the figures quoted in the manual's

Looking at the Lexus brand non of their vehicle's return good mileageper litre or gallon, but i suppose you cant have it all,

so enjoy!!!!!!!!!!! :) :) :)

[maneesh]

the sound of air rushing is a normal thing.

ur oxygen sensors are probably worn out, hence your high fuel consumption. get the diagnostic codes read to be sure. oxygen sensors wear out from 60k miles, and affect your fuel consumption in a BIG way..

I have to say that i was reading a manual on the LS400 and could not beleive that the GS300 was on par with fuel rating of the LS400

Even though the LS400 is v8 and the GS a v6.

that's explained because the V8 is a much more modern engine than the inline six of the GS range. plus, the gearing is much shorter on the GS (for quicker acceleration), plus the LS has the best aerodynamics of any Lexus model, also making it very quiet on wind noise!

[Simon Hornby]

the sound of air rushing is a normal thing.

ur oxygen sensors are probably worn out, hence your high fuel consumption. get the diagnostic codes read to be sure. oxygen sensors wear out from 60k miles, and affect your fuel consumption in a BIG way..

I have to say that i was reading a manual on the LS400 and could not beleive that the GS300 was on par with fuel rating of the LS400

Even though the LS400 is v8 and the GS a v6.

that's explained because the V8 is a much more modern engine than the inline six of the GS range. plus, the gearing is much shorter on the GS (for quicker acceleration), plus the LS has the best aerodynamics of any Lexus model, also making it very quiet on wind noise!

Thanks Maneesh - Sensors, diagnosis - sounds expensive!!! The car has done 148K and drives superbly. It has just passed its MOT and the emissions etc were fine. For the diagnosis does the car have to go to one of those overpriced tarted-up Toyota dealers or can any decent garage sort this. On my old BMW to do the ecu diagnosis you just hit the accelerator 10 in 5 secons and the dash board lights will flash any error codes. Is there a similar procedure for the GS300 do you know?

[maneesh]

sensors are not expensive, if you get them from the states, they are dirt cheap. 30 quid each for mine.

i paid 45 quid to get my codes checked, and they checked emissions too (which were within limits). just because your emissions are within limits doesn't mean the oxygen sensors are ok.

if you have a 1993 model, it's probably OBD1, so you may be able to get error codes displayed on the dashboard a la your BMW. my 1999 car is OBD2, so it needs to be plugged into a decent code reader.

Someone may be able to help on here, or try www.clublexus.com, which is a US site and has many more GS owners :D

[Ahhhh__Aristo]

Diagnosis won't show up a old/wearing out O2 sensor unless it's broken, but then you'd have the MIL showing and other symptoms. (there's only 1 on the MK1 GS, unlike 3 or something on the MK2, which also has OBDII diag, so that may show up a wearing O2 sensor)

21-26mpg is the norm, nothing to worry about. 32mpg?? possible I guess, but everything would have to be top notch and driven like Miss Daisy.

[dave1]

My Nov 96 sport gives 28/32 on run,16/20 local.Has improved since last service when plugs were changed.Done 133k.I dont drive it like an old lady though so I suppose it could do better figures.

[maneesh]

Diagnosis won't show up a old/wearing out O2 sensor unless it's broken, but then you'd have the MIL showing and other symptoms. (there's only 1 on the MK1 GS, unlike 3 or something on the MK2, which also has OBDII diag, so that may show up a wearing O2 sensor)

not sure I agree with you. my LS was obd1 and no MIL lights came up, but guzzled fuel. did the paperclip method to get the codes displayed on dash, and it displayed the code for problem with o2 sensor circuit.

[dave1]

Diagnosis won't show up a old/wearing out O2 sensor unless it's broken, but then you'd have the MIL showing and other symptoms. (there's only 1 on the MK1 GS, unlike 3 or something on the MK2, which also has OBDII diag, so that may show up a wearing O2 sensor)

not sure I agree with you. my LS was obd1 and no MIL lights came up, but guzzled fuel. did the paperclip method to get the codes displayed on dash, and it displayed the code for problem with o2 sensor circuit.

how do codes normally show up and where please

[ColinBarber]

1993 won't even by ODB-I, just the Toyota diags and if the engine check light isn't on then there probably won't be any error codes.

Given the age and mileage there are probably a few things that all add up to producing poor economy however depending on how you drive the mileage isn't too bad. 32 mpg would only be on a long motorway run, keeping below 80mph.

You could check/replace plugs, air filter, O2 sensors, Throttle position sensor, HT leads and cap, diff oil, transmission fluid.

Air rushing it is normal, the fuel system maintains a partial vacuum to reduce vapour emmisions.

[IanCornwall]

Hi Maneesh

Can you please explain the "paperclip" method, I havent found any codes or where they are displayed yet

[Ahhhh__Aristo]

You need to bridge terminals E1 and TE1 in the diagnostic port (paper clip, or wire) turn the ignition on, and the MIL will flash, say 3 times, then pause, then once, this would give you code 31.

If it flashes once every second, then no codes are stored.

[Guest]

Hi, I have recently bought a 1993 GS300 which I have to admit has grown on me. But I have to ask about reasonable fuel consumption. I have just filled up having done 282 miles it took 65 litres. This works out at about 21mpg. According to the Yahoo revue of the GS300 it should do about 26 and they a bloke flogging his on ebay at the moment claiming to be able to get 32 out of his. What is the real situation?

Now the car is due for a service so I would expect things to improve a bit after it's done. But there may be another clue to this poor performance...

When I open the tank to fill up there is the sound of rushing air from the filler cap. Is there a vent tube in the tank which could be blocked? Could this have a bearing on the fuel consumption? Any Ideas....

Does anyone know of any good Lexus technical web-sites?

Simon

I get about 22 mpg in my 2002 GS300 MkII that's done about £55k. I mainly drive from the house to town centre and back and drive like my trousers aren't on fire. Handling etc all feels normal and I've no little lights on to worry me.

Either our consumption is "normal" or we have the same style of clapped out old banger.

The air rushing in sound is because modern fuel systems try to maintain a partial vaccuum to reduce vapour emissions. All perfectly normal, but if it worries you, fill the tank more often so a lower differential pressure is created between fillings.