RX 450h - what is a 'normal' mpg return?

StretchedLexuses · April 24

Hi all,

Apologies that there are existing threads linked to this topic but I wanted to probe what a normal mpg return looks like on UK roads for a gen 3 RX 450h? I got a 2010 with 150k last week and whilst the car is generally very good, I have been a tad disappointed with the mpg. I've not done a long motorway run yet but on some mixed, very careful driving, I'm just about managing 30mpg. With such pronounced effort to be economical, I was hoping for 33mpg. What generally hits mpg hardest in these cars? Can a higher tyre inflation help, e.g. 40 psi? It's got 13 Lexus main dealer service stamps so surely it's well oiled and spark plugs have been changed (i know at least some have from the myLexus app). Ride is a bit choppy and suspect rear bushes have some play but keen to hear people's thoughts. Is 35mpg possible on a long motorway run with controlled speed?

Thanks all...

HPS13 · April 24

According to the Fuelly website, the average mpg for a 2010 Lexus RX 450h is 30.6 mpg from a sample of 74 vehicles so your 30 mpg may be correct.

With regards to tyre pressures, I would recommend following what the owner manual states. Naturally on a motorway drive you will expect to see your mpg increase in normal conditions.

StretchedLexuses · April 24

Fuelly quotes in American gallons though, which would imply 36mpg in a UK setting given the 20% difference.

HPS13 · April 24

Fuelly has a menu on the home page where you can select 'UK' for the units rather than the US option.

UK value is 30.6 mog.

Stevo11 · April 25

I bought mine in Jan, 4800miles since, Avg 31.44mpg ... I found it took about 4 weeks for me to adjust to how to drive these for best mpg, ECO mode on/off doesn't seem to matter.

On the majority of my longer distance journeys I pull either a boat or a tall covered trailer so factor that in.

60mph+ really hits mpg, scooting around town it'll easily go to 34mpg average.

My best over a tank was 35mpg.

Spottedlaurel · April 25

Unless you're doing 50-55mph on a motorway and can manage doa bit of coasting it's unlikely you'll see an improvement there. At 70 you'll just be running on the petrol engine all the time.

I normally get an indicated 34-35mpg, on a mix of 50mph A-roads and tootling through towns and villages at 20-30mph. That's after 5+ years of getting used to it.

Cypry 1 · April 26

2010 RX450 Premium 95000mls

My average is about 31mpg on local journeys but on a run I have had as much as 36/37 mpg.

However please be prepared for a drop to 27/28 mpg in winter.

Bear in mind that the size of the vehicle, weight and the V6 engine but this is still better than you would get with other V6 SUVs.

StretchedLexuses · April 26

Thanks for the intel. I'm getting 29mpg on mixed driving so far but on the more local and extra urban side (few runs above 50mph). Does make me think that maybe some cells are failing as I've been trying to make the most of engine braking and general braking too, and certainly havent been heavy footed. Feel like I should be getting 32mpg. Spark plugs were last replaced by Lexus main dealer just over 3 years ago. Does a failing 12V Battery make any difference? Haven't checked tyre pressures on the 19inch wheels yet but the ride quality is absolutely shocking IMO. Constant vibration and judder with every road contour eliciting a reaction, even on the motorway. I read about the firm ride but this is kind of ridiculous. Rear bushings had an advisory so perhaps that's part of the problem there? Comfortable as the seats are, constant cabin movement grates.

Stevo11 · April 26

I don't think the Battery will make much difference tbh and from what I've read, very unlikely to fail. Finding the sweet spot between accelerating and coasting on the pedal (where it keeps the speed constant) took me a while to find.

Have you air suspension? Which brand shocks are installed?

MUDGUTS · April 30

I get 40-42 on a run from Chesterfield to Hampshire/Surrey regularly. 95% motorway. Speed between 55 and 75. 2009 RX450h 155k regularly serviced. I think Tesco 99 or Shell V-Power helps. 38.5 would be my worst on this journey. 42.5 best. That’s average of 42.5 on the 400 mile return journey.

You have to totally minimise acceleration and use of brakes. Obviously this is not always possible. If you plan the braking that is required effectively that will help maximise regenerative braking; keeping the needle inside the blue zone but not letting it drop to the bottom or any braking past that will not be regenerative. The more you can coast when meeting slower traffic the better. I don’t use the ‘eco’ setting at all or A/C. I think it’s less generally if wet/dark etc.

StretchedLexuses · May 14

Just wanted to update people on this. The first long (over 15 mile) journey I did in this car I got an MPG of 38, on a 120 mile trip from West Yorkshire to North Wales. Not too shabby. It was mainly motorway driving and I probably averaged 64mph on the 70mph stretches. I was making a conscious effort to be economical but without being rooted to the slow lane behind lorries. Not bad for a 14 year old car. That same tank is still achieving 36.5mpg now, with mixed holiday driving, again being light on the pedal but not to the extent that it becomes tiresome. I find it hard to believe anyone could get more than 40mpg - unless on gently undulating motorway sections - but I was ecstatic with 38.

GSLV6 · May 15

I've put up many thousands of miles on my RX3 and MPG is no-where near as stated, which is based upon flat, uninterrupted motoring. My long term average from a 2014 car has been 28mpg and I do drive to get the best I can from it. A lot depends on topology of where you live and drive. If you're in a hilly area, you will get less, as it's a heavy vehicle. It makes a huge difference on economy. For example, one of my runs is cross country, mainly flat, 90 odd miles each way and if driving carefully but up to the posted speed limits, I can get 34 to 36mpg on that run (no motorways, all A roads). For motorway driving between 30 and 32mpg is about right at a steady 70mph but will hit mid 30's if you drive a bit slower at 60 to 65mph. You get no benefit from the hybrid system at motorway speeds. For short trips where the engine has only just gone through a warm up cycle (say a few miles each way) you're looking at nearer to low to mid 20's. In town, it's much better if you can be gentle on the throttle and keep it in electric mode where it will impress with far better economy up until it needs to recharge the Battery (usually a mile to a mile and a half), but even then, you should be in low to mid 30's overall over a few miles.

Basically, they like to be at a constant speed and load with the needle in the economy/charge section of the dial. Any increase in load (even gentle hills) will see it into the power section where for peak torque and response, the revs will pick up and you'll drink more fuel.

Overall, 28mpg is a reasonable long term average for a 2.2t vehicle with a 3.5 litre engine. By comparison, my old S60T4 petrol volvo averaged 22mpg, and my E46 BMW 2.5 petrol averaged mid 20's. The older petrol only V6 3 litre GS cars woud get considerably more (up to 45pmg) on a motorway run and less (26 to 27mpg combined) when on combined cycle.

If you have to worry about fuel efficiency as part of factoring in running costs, I'd say it's better to look at something smaller and lighter and slippier through the air. You won't better the above figures by much longer term.

GSLV6 · May 15

15 hours ago, StretchedLexuses said:

Just wanted to update people on this. The first long (over 15 mile) journey I did in this car I got an MPG of 38, on a 120 mile trip from West Yorkshire to North Wales. Not too shabby. It was mainly motorway driving and I probably averaged 64mph on the 70mph stretches. I was making a conscious effort to be economical but without being rooted to the slow lane behind lorries. Not bad for a 14 year old car. That same tank is still achieving 36.5mpg now, with mixed holiday driving, again being light on the pedal but not to the extent that it becomes tiresome. I find it hard to believe anyone could get more than 40mpg - unless on gently undulating motorway sections - but I was ecstatic with 38.

Well done, you're doing exceptionally well to achieve those figures but check your trip computer against topping the tank up, then brimming it after a long run to see how the computer compares with actual. Mine usually is a little optimistic.

StretchedLexuses · May 17

Thanks. I also got 39mpg on a 25 mile journey on the next refill, which was mixed driving at about 55mph overall. However, in the interests of fairness, the return 120 mile journey is much more 'up hill' and I achieved 35mpg for that leg, again with carefulish driving but not stupidly 'slow'. Average of 65mph. Take your point on trip computer accuracy.

MUDGUTS · May 25

Recently achieved 44.3 on a run from Chesterfield to Gatwick area. Wasn’t particularly trying to get high mpg.

I’ll do a ‘brim to brim’ check in a few weeks. I’ve had the A/C topped up and now that’s switched on and set to auto in terms of fan speed, mode and recirculate etc. will report back.

Unless my car’s computer is way off I think it’s just a case to driving these cars a very specific way to achieve max mpg. Nothing much to add to my previous post other than if you were to imagine you have no brakes or the brakes of a 1960s heavily laden family car on a wet road, that might help. I believe they are very sensitive to technique and bear in mind they are heavy. Changes of velocity either way always use a lot of energy and the trick is to minimise those changes. The drag at motorway speeds will be greater than something more aerodynamic but I don’t think that’s a particularly big factor unless you are really travelling fast. Drag is a velocity squared, so 5mph faster at 65mph will be consuming more extra fuel than 5mph faster at 60mph, if you take my meaning.

Not wishing to sound pathetic but as an ex motorcyclist, someone who has lost their licence for speeding (over 110 on motorway), regularly saw 140 in my old GS300 and 150 in my LX400… Bear in mind that most motorways are flooded with morons, retards who can’t drive, speed cameras and just don’t move that fast so we may as well go with the flow and keep our fuel money for whatever takes our fancy.

StretchedLexuses · May 25

I was wrong about 40mpg being impossible. 44mpg achieved on a 14 mile trip on good rural A roads, straight from a refuel using Shell V-Power. Undulations were favourable but even after return leg a few hours later, it was still on 40mpg. Pleased with that for a close to 30 mile journey!

MUDGUTS · May 25

I seem to get the best mpg from V Power.

Spacewagon52 · May 25

The hybrid system and CVT gearbox lends itself to driving economically. After running the car for a few months this will come naturall. Driving a hybrid to get the "best" out of it does take practice.

People who moan about the CVT gearbox and fuel consumption, tend to be heavy footed with the accelerator. The RX hybrids can shift if you need them to but as Phil (Mudguts) says, those opportunites are becoming less for the factors he states.

StretchedLexuses · May 25

I meant to say earlier that I didn't check the tyre pressures when I first got the car...which was stupid. When I did, I discovered they were at 29psi! I run them at 38psi now, and the car drives soooo much better now.

GSLV6 · May 26

Depending on tyres fitted, I think the default for the 19 and 20" 235/55 tyres is 33psi unless heavily laden. You'll reduce rolling resistance a little with firmer pressures but will tend to wear the tyres more.

Gedwood · May 26

I've owned my 63 reg RX450h for a year (first of the updated shape). When I first got it, I struggled to get in excess of 25mpg average. I soon learned, a smother lighter right foot to be a friend. I had my eureka moment when I found the 'eco mode' setting and it now stays on that mode, with the green light lit on the speedo. I read that these gearboxes work most efficiently when you accelerate smoothly to maybe a mile or two beyond your required speed, then ease off. This locks the gear to the maximum and optimum gear ratio. Cooler weather now returns 29-35 mpg. Yesterday, (17-19 degrees), a return trip from Tredegar to Swansea, along the speed restricted Heads of Valleys rd, and trying not to exceed 60-ish mpg too much elsewhere, I achieved 42 mpg. I run with 39lb all round tyre pressure - albeit on horrid Dunlop Sport Max, 235/55/19 (my pref is Goodyear efficient grip, which will be the next set). Dunlops appear to wear the outside edges a touch, despite this slight over-inflation and an expensive 4 -wheel alignment.

StretchedLexuses · May 26

6 hours ago, GSLV6 said:

Depending on tyres fitted, I think the default for the 19 and 20" 235/55 tyres is 33psi unless heavily laden. You'll reduce rolling resistance a little with firmer pressures but will tend to wear the tyres more.

Yeah I just prefer the feel. I know the tyres will wear faster but my annual mileage is no more than 5k so it's a trade off I'm willing to make.

mikey2001 · May 26

I've also found that fuel comsumption is heavily affected by ambient temperatures, with a marked difference now we are heading into summer (I tend to average around 38mpg in summer, but only around 30mpg in winter).

Illogan · May 26

After 4 years of driving our 2014 F-Sport, it's currently on 33.6 mpg (combined winter/summer, 95% about town, 5% motorway)

GSLV6 · May 26

A lot depends on the geography of where you live too. Those living on the flat will usually see significant gains in economy with such a heavy vehicle. For me, living in a hilly area, best you could hope for would be a long term average of 30mpg (my 2014 F sport averaged between 28 and 30mpg long term, winter to summer). Only had my RX4 a few days but so far showing low 30's but each drive sees a slight improvement (currently on just under 32mpg). It's doing a little better than the older one.