map0824

I just took a trip and got 22 to 24 MPG. I believe I was getting 28 MPG with the original tires. I had PAX so when they wore out I replaced the wheels and tires. Instead of the original 17" PAX I have 245X45 18". Would this drastically affect my gas mileage? Could I have another problem I am not aware of?

oo7spy

You were not getting 28 mpg average on the PAX wheels unless they were WAY overinflated and/or you were ONLY driving hwy non-stop. 22-24 is on the high side of average for the RL. Many of us suffer(ed) with 18-19 or lower.

cmx168

i just picked up an rl 2.5 weeks ago. so far im averaging 17.5 mpg and I'm driving like a grandma.. its super frustrating so far because I've mostly been on the highway and im using premium fuel. i just replaced the air filter and inflated the tires to 37/35. also plan on using techron and possibly swapping out the spark plugs. cars got 95k miles but so far this is extremely irritating, i would be happy to get 22-24 lol!

oo7spy

Is it possible your brakes are sticking? 17 mpg is expected for city. 28 is completely possible for 100% hwy. The RL should just get better with time. Make sure all of your fluids are new, tranny, transfer case, rear diff, and engine oil.

Türk

My Legend burns 19 litre/100 km.
I think it's about 12-13 mpg.

My course is generally 3 miles morning, 3 miles evening.
I think it's normal such a sized car, right?

Diesel Renaults goes about 40 mpg.

=)

cmx168

i haven't replaced all the fluids just yet but I did look at the previous owners maintenance and he definitely kept up with the regular service intervals. seems like the 2005 model did only tend to average 18-19 combined though.. anybody else with an 05 chime in?
i think i'll start with the the spark plugs, and then move onto swapping out all the fluids. transmission and diff fluid were switched out in the last 15k or so i don't think i need to do that..

oo7spy

It may also be worth looking into the fuel injectors and PCN update from the dealer. I think there was a TSB on it.

map0824

I filled up yesterday with Shell V Power 93 and today I put in Techtron. Drove for an hour on the highway. I reset my "B" miles per gallon while I was driving. It said 24. I will let you know as the tank runs down if I see better.

oo7spy

Next time you fill up (assuming you filled up completely last time), take the number of miles driven and divide by the gallons filled. Then, compare that to your meter. I doubt it's very far off, and usually the meter is higher than actual. However, this will rule out meter error.

Still, 24 is awesome and 28 is next to impossible.

HEAVY_RL

iTrader: (1)

LoL, I get great mileage when I reset it while driving after I fill up.

these threads exist on every board all over the net and the reality is that no one has the golden ticket

Happy post whoring.

justnspace

iTrader: (1)

Since these cars are getting older and higher mileage, I just want to point out that 02 Sensors DO GET LAZY!
and if lazy, might contribute to poor gas mileage.

**Just a consideration and you shouldnt go out and buy a new 02 sensor just to test!

phishfood

I hit 29-30 on the highway. 70MPH max.

All it takes it not using cruise, hit the gas a few times to pass, etc., decide to go 75, and wham I'm down to 25.

Check tire pressure. Take a trip, use cruise, don't touch the gas, imagine your testicles are in between your foot and accelerator, keep to speed limit or 5 over max, if you hit heavy traffic or congestion slow down so you are never needing to pass or slow for guy in front, over inflate a smidge (35 all around) ... see if gas mileage goes up.

poppintec

30 is pushin it I think the most you can get on pure highway driving is 26-28 max

oo7spy

I have had the MID tell me 28 after resetting at a truck stop and averaging 75-80 on non-stop highway. That was until I hit construction 100 miles later, and I immediately dropped to 26. Keeping in mind that the MID was always 0.5-1 MPG better than actual for me, I was still impressed for the speed and figured 29-30 could be possible at 65-70.

To expound on Heavy's point, resetting the MID after you have left the stop is not in anyway an accurate method.

dahatter

I have 2005 with over 200,000 and my last trip from Chicago to Detroit I average 25 mpg running at 75mph.

HEAVY_RL

iTrader: (1)

oo7spy

I reset it once just before rolling to a stop light. 88 mpg!

Sitting at the stop light, the countdown started. I think it was around 60 when I hit the gas and 30 a block later.

Türk

Here is my 30 km highway record.


It's 30 mpg.

My avg speed is 90 kph.

(=

oo7spy

Looking at that gives me a headache.

cmx168

ok, so i just took a trip down to portland. refilled and drop a bottle of techron in. drove for about 110 miles straight going about 70-75 and i'm getting 26mpg. this was driven almost exclusively on cruise control so that means my car tops out at 26mpg which is fine.... apparently my city driving just destroys the Mpg's though. i guess we're just going to have to see if the techron does any magic. 007spy, what is this PCN update that you speak of? the only update i've heard of has made gas mileage worse. nonetheless i'll provide my vin to the stealerships to see if there are any updates i need to make.

oo7spy

What are your tires pressurized to? OEM spec is too low for the RL IMO and is intended for comfort over efficiency. I always ran 36 cold, and I know my pal Heavy runs in the 40s.

I would have to search for the injector and PCN info, and that won't be until Mon. I don't know if it was a service bulletin or a TSB, but you should be able to find the info.

map0824

After the tank ran out I was showing 22 but I had to do a lot of city driving one day. I did notice that the engine is idling better. The car seems quieter and more responsive. My cold tire pressure is 38. I have Primewell PZ900 tires. Just filled up again with Shell V Power 93. Maybe in a couple of weeks I will do another Techtron since it has been 7 years and this is the first time I have tried to address this.

Türk

Why?

oo7spy

Ultra High Performance tires are definitely going to dock you MPG when compared to a touring tire. I don't know how well your PZ900 grip, but you can easily expect a 1-2 MPG difference.


Turk, too many conversions to our dumb system.

cmx168

soo just completed my trip back from portland.. also changed out the spark plugs... my combined average has risen up to 22 mpg. if i can get that combined from here on out then i'll be satisfied, but again this was wiht almost exclusively all highway driving. i'll see how things turn out now that it's back to a normal work week. i don't think theres anything else i can do to the car at this point tom increase my mpgs... lol.

oo7spy

One other thing is that winter gas doesn't perform the same as summer gas.

TampaRLX-SH

Also ethanol ratios have risen since the 2005-08 RL was EPA rated.

When my RL was new it was easy to find no ethanol gasoline, and when not, mostly 10% ethanol (E10). Now with E15 the norm, I generally see 2 mpg avg less than when my RL was new.

Add tire changes, winter / summer fuel mix changes, etc.....

cmx168

probably a dumb question but i'm going to ask it anyways... if the 2nd RL had stayed largely the same besides some cosmetics changes, why can't we swap out our transmission for the 2011 version with the extra gear? anybody?

TampaRLX-SH

I do not know that you cannot...money makes many things possible.

But the 2009+ RL has a 3.7 V6 and the 2005-08 has a 3.5 V6.

There may be compatibility / tolerance issues rooted there.

cmx168

yeah, but isn't the 3.7 and the 3.5 the same engine just bored out a smidge? pretty sure that's the case.. this would definitely be something worth looking into especially if and when your transmission goes. Somebody please chime in!

HEAVY_RL

iTrader: (1)

Not a dumb question but a lot to consider starting with the mounting brackets and thread casting on the block to the ECU and any additional wiring.

If you were to do a little research to back up your question you may be on to something, but I doubt you will find someone with first hand experience.

phishfood

30 is quite do able. Been hitting it on many trips.

Here is pics of trip from last week.

30.3 MPG over 399 miles.

Note 66mph avg including about three stops. Mostly had it cruising 70,75,60. Temp us low here but that was pulling in around 9pm there was warm weather earlier in day.

BDoggPrelude

Headed up to Glenwood Springs from Denver for a couple days with the wife and kiddo this week. It was about a 300 mile round trip. Denver is about 5,280 feet in elevation, Eisenhower Tunnel is the high point at 11,158 feet and Glenwood is about 5,700 feet on the other side of the mountain. Averaged almost 26mpg and 56.5mph with the adaptive cruise control doing most of the driving. Not bad for a semi-loaded RL with snow tires on it at this altitude.

F35PHIXER

who cares you're driving a nice sports luxury car... ENJOY !!!

06RL/NBP

I am getting 14MPG in all city stop at every corner driving.