Well my LS seems to be acting up a bit.
On idle, I can smell a bit of fuel when I step outside - a faint smell but it is there.

However on a full tank I'm getting around 180 miles/300ish KM and I feel this is quite low? My previous LS used to push over 225-235 miles on a full tank so I feel something is wrong here.
Any suggestions into what to check. I recently changed the air filter and am thinking to jack the car this weekend. Also noticed a slight leak of oil within the plastic covers, I believe this is gear oil as shifting seems to be a bit tougher within the gears (such as Neutral to Drive/reverse).

I'm more worried about the fuel issue at the moment. Fuel filter to be changed shortly too!

 

I would check that out as soon as possible. My 2003 LS430 gets about 450-500 miles to the tank with 91 octane and about 350 to 400 with 87, but it got 300 before i fixed my blown head gasket. May be an oxygen sensor if its burning that rich.

 

A couple of thoughts. There is no way to judge what's going on by how many miles one gets to a tank--what happened over the 22 gal? Was the driving stop/go? Highway? A combination?

Secondly, there is no relationship between octane, and mpgs. Octane relates to predetonation, not goodness, power (of the fuel--say you use 93 in a car designed for 87, like many GM vehicles), mpgs, etc.

I know my car, and to my job, I will get on avg. 19.x mpg. I have so many routes depending on traffic that the route does affect mpgs, because of the degree of stop and go traffic. But over 5-8 working days, the mpgs will gravitate to 19.x. Week, after week.

The way imho to level the playing field, is to get onto the highway, and when you reach 65 mph, set the cruise. Now, reset the mpg computer, and let it go for about 30-50 miles. 50 is better as it boosts the validity of this test. If this were my car, I would be seeing > 27 mpg, and 28.x mpg. The longer it could keep going, the more likely I can yield 28.x.

The likelihood of driving under the same conditions for 22 gal., is not good imho, which is why you need to see what your mpgs are under a controlled situation...my .02. Good luck.

 

Given the fact the LS430 requires 91 minimum since it's a higher compression v8, i would (and do) use it. A good ol' seafoam tuneup could also be great in restoring that gas mileage.

 

93 is sold where I am, so I use it. I fight the high cost by going to the warehouse clubs. But I'm pretty sure premium is "not" required. On my Maxima, premium was recommended, but I ran it for 20 years on regular 87. When the knock sensor failed, I switched to premium until the knock sensor was replaced. If you don't use premium in the LS, you won't achieve (for 2006) 278 HP / 312 ft. lbs.

Dag I didn't realize I had only 278, for whatever reason thought it was 290 and only torque was lower due to the new measurements....

 

I have used a mix of premium and regular over the years with no difference between the two grades of gas except for a very few times on extremely hot days and while going up a long hill on that specific hot day I have felt the engine knock. I almost always use regular gas on long road trips particular if the roads being traveled are flat. The V8 on the LS is just loafing along at 75-80mph on the interstate and it will run perfect on regular gas for that kind of trip. I mostly run regular in the winter but in my area premium isn't that much more expensive so it varies. For a long trip up to Colorado and Wyoming this summer I'll run premium in the mountains in that heat.

 

Well I am filling with a 95. I had my doubts with the O2 sensor and running rich but I'll get down to the problem.

Driving wise, the first drive was a bit aggressive as I could not get used to all that power (was driving an ES and another 2L crap mobile so this was a joy) but then I decided to become an adult and actually drive normally after the next fuel stop. Filled it to the top and been driving and from owning another LS, I feel the fuel consumption is quite low. It is a mix of highway driving, start stop traffic and normal cruising. I live in a small city and drive city to city so think mid city/hwy driving - a mix of the two.

Seafoam could be a great tip, I think the cats may be blocked/need to be cleaned? Perhaps this could be an issue (carbon build up???). I just recharged the AC gas as well. I thank you all for all the tips you've given me and hope to attempt to fix this issue SOON!

 

So I just realized your getting 8.8 MPG average, but I know your pain, my 02 Jeep liberty got 13 MPG at best, and surprisingly the LS weighs more and gets about 21 Average and has a V8 instead of a V6

 

City driving chews out your fuel consumption in a big way. My 00 LS430 is hopeless on gas around town, but you should be able to get at least 700 km to a full tank on highway miles. The best tank average I've ever had was a 9.8L/100km and that was driving with the patience of a saint. Anywhere from 10-10.8L/100km is normal for highway usage, while city driving you'd be lucky to see under 15 or 16L/100km. Definitely use a minimum of 95 octane though, my LS runs like a sack of garbage on 91 (although our 91 is pretty poor quality), but I normally use 98 or 98/E10

 

When my wife drives, she does not go on the highway, and she does not drive with an egg between her foot and the pedal, and she comes back with 14.x consistently. My buddy surmises she drives like he did when he had a LS. Because when I got it, he told me 14 city. My 19.x has a tiny tiny bit of highway or 40-50 mph (we're talking maybe 10 miles tops, out of 50 miles per day, or 20%).

Again, imho you cannot tell anything about your car by looking at miles per tank. At the same time, if you get 15 on the highway after 50 miles, there is something wrong.

With gas really expensive, I see the delta between regular and premium at the warehouse club yesterday was 22 cents, down from 40. Price elasticity of demand.

 

My best tank average is 9.0L/100km, repeatable over the same 500km drive between 9.0 and 9.5, and only in that one direction (Toronto to Ottawa). Going the other way (Ottawa to Toronto), it's 10.0-10.5. This is assuming speeds of 100-120km/h. At 130-140km/h, I strongly suspect that 10.5-11.0L/100km would be your fuel economy, which is still excellent in my opinion.

Official 2002 LS430 Canadian brochure says the highway fuel economy is 8.8L/100km, but I have never averaged under 9.0 on an extended highway drive and don't believe that is a realistic number.

I don't know if the gas in Toronto gives better mileage, or if the gas in Ottawa gives worse mileage, or if the Toronto to Ottawa drive is slightly downhill and Ottawa-Toronto slightly uphill. I use Costco Premium and Shell V-Power when Costco is out of the way, and both are Top-Tier certified.

In-town driving is significantly worse, winter or summer, any short or long distances with starting and stopping - 13-16L/100km is normal in-city fuel economy for me. If you are getting less than 300km on a full 84L tank, that means your fuel economy is closer to 28L/100km, which is atrocious.

In my opinion, something is very wrong if you are seeing over 18L/100 in city driving without extended idling, or you are heavy-footed. Assuming that the problem may be car-related and not user-error, plug in Techstream, run the full health check, and if you have no DTCs, check all fuel/air/intake-related numerical measurements, including fuel trim, O2 sensor efficiency, coolant temperature, incoming air temperature, etc. Compare with other people's numbers and perhaps you can identify why your mileage is so bad.

 

91 here is garbage. I'd only use it in a car I do not care about. I would not even put it in a friends car lol. I do not see the point of it but hey whatever makes people happy. Owning a previous LS, I feel the fuel gauge goes quickly but what was bothering me was the faint scent/smell of petrol when the car is on idle... much work to be done!

This is what is worrying me... on the highway it isnt that much but the fuel goes like this was a LX! I will start to diagnose the problem, part by part. Just been running about with work and all.
As for my previous LS, lets say I am heavy footed and I do press when I can - LOVE the feeling of the flying lounge just cruising past all the other cars. Mmm! But I used to get around 330-335 miles on the previous car, I cannot even get 200 miles on this one! Last fuel to current (just under the 1/4th mark towards empty) shows around 272 KM done on... I suspect 320-350km at the best till she runs on empty. Perhaps a fuel cleaner or something is required as well. As someone suggested, seafoam!

At the moment it seems I’m getting lower than that. On a full tank I can’t get past 300-350km on a full tank? That is what is worrying lol. I honestly think it’s the air/fuel ratio or something may be leaking OR is blocked. I have not had time to check the car/drop it at a garage but soon.

 

UPDATE:

So the mechanic and I pondered over... for hours trying to resolve this. Here is where we got to.

I've noticed a fuel line hose was quite weak and it could easily come off, that got replaced! I believe there was some vapors leaking to the side of the car.

The canister will be cleaned and I got a pack of fuel injector cleaners that I'll put in when it's out of the garage. Furthermore, suspension/bushings and what not have been replaced and I've noticed my gear oil was considerably low AND pretty much black! Was not impressed but hey, previous owner says they've always maintained it and it ran in good shape, ugh.

New oil + new gear oil (with filters), new shocks, engine mounts and a new air filter alongside the fuel filter. Hopefully the fuel cleaner will do it's job. Cant wait to ride it... I actually miss it!
Finally, tires need to be changed, I've noticed wear on them and they're a sub brand and I'd like to actually get new tires, align and balance them so it drives like a cloud.