Fury63

GTF

I'm lucky to have a friend who is an expert engineer in energy-related industries, now retired, but remains a consultant for major energy/transportation companies.
His advice:
Use premium synthetic oil. He uses Mobil One (0-20 unless recommended otherwise) in most of his cars.
Use "Top Tier" fuel, especially if using regular grades. Top tier mostly impacts 87-89 levels where some companies restrict additives to premium (91+) grades.
Use the recommended fuel...if manufacturer recommends premium, use premium. Efficiency (mileage and power) will be adversely impacted by lower grade fuel. Using regular might save money, depending upon pricing premium.
There is no significant benefit using higher than recommended octane levels, as long as it's a top tier fuel.
Avoid ethanol. The most common (10% blend) will reduce efficiency (mileage/power) 3-6%, depending upon application. Unfortunately there usually is a slight cost premium even considering the efficiency advantage.
(My friend's cars total about $1.2 million, so not much concern for him)
Ethanol blended fuels also have been the source of significant problems when used in older automobile engines, as well as most small "garden tool" motors (weed hackers, chain saws, etc.).
Note:
Ethanol free fuel availability can be found on "puregas.org" website...availability is becoming extensive in most states. Unfortunately states owned by the corn/ethanol lobby (i.e. Iowa, Illinois, California) have succeeded in restricting choice/availability.
Ethanol began being sold as an environmental solution, long since debunked. Not even Al Gore continues to support ethanol. Now it's just a tax-fed money machine for the corn/ethanol industry and there related political contributions. IMHO.

skarface

"There is no significant benefit using higher than recommended octane levels, as long as it's a top tier fuel."

The only thing I would add to that is in the case of the 2.0 4 cylinder turbo, Honda recommends 87 in the accord and 91 in the RDX. Dyno tests on the accord showed a slight boost in the power when using premium fuel vs 87. I'm thinking Acura just used premium fuel in their tests to be able to claim the higher power numbers and it's just about the same engine, so higher octane actually gets your Honda the Acura numbers.

MarineOne

This is the actual website:
https://www.pure-gas.org

R. White

Ethanol free fuel availability can be found on "puregas.org" website...availability is becoming extensive in most states. Unfortunately states owned by the corn/ethanol lobby (i.e. Iowa, Illinois, California) have succeeded in restricting choice/availability.
Ethanol began being sold as an environmental solution, long since debunked. Not even Al Gore continues to support ethanol. Now it's just a tax-fed money machine for the corn/ethanol industry and there related political contributions. IMHO.

__________________________________________________ ________
How much is this ethanol free gas ? It looks like all racing fuel in my area ( MA)

MI-RDX

Same around here locally - it's either at a marina (tough to pull your car up to the pump) or 100+ octane ($$$$).

GTF

Most stations offer either E0 (Ethanol free) OR 10% blend on their premium (91 or 93 octane) gas. Filled up this week at $2.99 91 E0. The blend available at another brand at $2.89....so E0 was (here) an additional $0.10/gal. I live in relatively low-priced market. About 30-35% of the stations around me have converted to E0 on their premium, but keep 10% on their 87-89 octane. Note that marine and aviation fuel does not allow ethanol...

GTF

I haven't researched the complete specs of the RDX engine, but I suspect there will be upgrades to the RDX as there were in the Honda Civic type R (306 hp, 295 torque). The type R gets substantial internal hardware modifications as well as higher flow fuel injectors, higher flow turbo, more aggressive tune, etc. at same 9.8 compression ratio.
Note I said "any significant" increase using higher than recommended octane rating. There could be very marginal increase as the timing approaches maximum allowed. Nothing to justify the price premium.
Using premium in the Accord motor will not result in a 20hp increase.

neoshi

Heh come to California. E10 everywhere.. *crycry*

TxLady

Hondaluvr29

I'm no mechanic either but after reviewing multiple reports from consumerreports and fuel.gov or whatnot. 87 might slightly affect performance and EPA but is considered neglible compared to the price you pay for premium. There is also NO reports of long term reliability as it does NOT damage the engine(government website). When asked Luxury automakers, they have also stated that premium MAY Dec performance and EPA but have never claimed that there will be any damages. This is all for cars where premium gas is RECOMMENDED and not REQUIRED. I believe it is also true that there are sensors that let's the ECU know what octane gas you are using for modern cars that calibrate accordingly, and I would be very surprised if the 2019 RDX doesn't have it. I do believe that luxury automakers who recommended premium say so, so that the driver gets the best experience possible with that car. The engine and turbo is derived from the type R and accord. I don't know how different the engine is from the accord but the accord is recommended for Octane 87. So people who are claiming it will damage these new turbos think again. Cars and the entire gasoline automotive industry have been around for a while and know what they're doing. If they really thought you NEEDED premium fuel they would make sure to let you know of it.

The times I would definitely use premium just to be sure is summer, towing, any sort of knocking. (You will know early on, a couple knocks won't damage the engine)

Now why am I stating all of this? Because I'm the type of guy who will pay 50k for a brand new 2019 car but refuse to pay the extra for premium fuel if I don't have to.

MTD

As a follow up to this...

My RDX now has about 1000miles (1600kms) on it and the last tank showed 23mpg (10.3L/100kms), same driving situation, mostly city and rural low speed highways, Sport and Sport +, 91 gas. So in my case, fuel economy is getting better. Wife is doing a few longer highway commutes this weekend, so I'll be sure to report back in a few days.

romer

Hou-RL

My mileage is averaging 21.3 MPG which up form 19 MPG.

TxLady

MI-RDX

And to get accurate numbers you have to insure that you fill the tank to exactly the same level every time you fill. The only way to insure that is to fill at the same pump, park in exactly the same position, insert the pump nozzle the same amount and stop filling when the pump automatically shuts off (and hope that between fills no adjustments or maintenance was done to the pump that would affect it's operation). Anything else and you're just 'guestimating'. Over time (as in many fill ups) the errors will tend to work themselves out but there is no way calculating mileage on a single tank will be correct unless you're extremely lucky.

IMO, for a single fill up, the car is calculating closer than I can because I don't do what's necessary to get accurate numbers - while the car is measuring fuel flow vs miles driven using consistent measurements.

Fury63

TxLady

romer

skarface

ednigma

I tend to agree with MI-RDX,
The cars computer measures fuel flow directly through injector on time (knowing the rated fuel flow) and the miles driven as reported by the revolutions of the wheels (which can be affected by tire diameter as a function of inflation pressure). This is a very simple calculation for the cars computer to do. Unless you subscribe to the the conspiracy theory that the car inflates the MPG to make the owner happy--what if it got out that Acura purposely programmed the computer to round up fractional miles and round down fuel used in order to inflate MPG? It would be class action lawsuit and damage to Acura's reputation.

When you calculate your MPG by hand, you have the same possible error in miles driven due to tire inflation so that cancels, then you have possible errors at the pump calibration (these are supposed to be certified by the state regulatory agency, but how often do they check?), you also have auto shutoffs that don't always shutoff at the same consistent point (it's basically a low tech mechanical pressure sensing system), I know many times the pump will shut off a few seconds after I begin to squeeze the trigger because the fuel splashes against the gas tank filler pipe and some gas is sucked into the sensing hole, or if you hold the end of the pump nozzle tight against the fill pipe it restricts the air flow into the sensing hole and again premature shutoff. In both of the cars I regularly drive, I have used the technique where I fill the tank carefully so that I can actually see the fuel in the fill pipe (not recommended for several reasons) and checked against the computer and was always within 1/2mpg for both a 2002 Lexus and a 1997 BMW.

The most accurate way to measure MPG is with a auxiliary wheel (looks like a bicycle wheel) attached to the vehicle and a calibrated container of fuel plumbed to the fuel pump. I don't know if they bother with that anymore, my cousin described it to me when he used to work at the GM tech center in Warren, MI. Now I think all the car manufacturers estimate their MPG and let the EPA do the testing for the official numbers.

Just my two cents - YMMV

MI-RDX

I wasn't challenging you, just pointing out that in order to do the manual calculation it's imperative to accurately determine the amount of fuel used - and for all practical purposes that's the most difficult, if not outright impossible, aspect of the process.

The only way to accurately determine the amount of fuel used would be to install a device between the gas tank and the engine to meter the actual amount of fuel used.

To demonstrate how critical an accurate measurement is consider the following:

250 miles @ 23.5MPG = 10.6383 gallons
250 miles @ 22.5MPG = 11.1111 gallons

The 1 MPG variance is the result of a difference of only 0.4728 gallons of gas - less than 7 8 oz. cups (or roughly 5 cans of beer/pop/soda). Stated differently, a measurement difference equal to just 1 can of beer would result in a MPG calculation differing by 2/10 MPG. This is over a 250 mile driving range - for shorter distances the measurements are even more critical.

Many automotive writers like to do 100 mile road trips for their MPG 'testing'. In that scenario a 12 oz. (1 can of beer) measurement error would result in a 1/2 MPG difference in the calculation.

And that's why I put more faith in the calculation done by the vehicle versus anything I (or anyone) can do at the pump.

billyt1963

I have tracked my gas mileage as long as I have owned a car. My current car is a 2012 TL SW-AWD. As of late it has seem more in town driving, so the gas mileage is really suffering. Just to go along with car estimate vs calculated, I thought I would show 10 recent fill-ups:
Calculated Car estimate
19.9 19.9
20.8 19.9
20.8 21.0
19.0 19.5
23.3 22.5
21.0 21.4
19.6 19.6
20.4 20.2
19.6 19.4
19.4 19.4

I am not precisely consistent on fill-ups of always stopping when the tank shuts off, but I also don't try to fill the gas tube up either.

Billy

Sorry for the formatting. The site didn't like the table I pasted in and I had to edit the two lists.

Notte

I guess I do appreciate the information from this thread, but, lets be honest, people aren't buying RDX because of MPG. This thread should be about posting your driving experience versus mpg. I feel like I'm on a Hyundai Ioniq Hybrid forum where everyone is giddy about posting their MPG.

Blah! lets talk about the awesome RDX driving performance instead of <insert elevator music> "MPG".

Wake up and live a little, damn people

Fury63

ednigma

With all due respect, why are you thread bombing? This thread is about MPG, so naturally, we are going to debate aspects of real MPG, which can be difficult due to the newness of the engine (pre-break-in). MPG goes to Total Cost Of Ownership. Bad MPG can also be a sign of a mechanical problem. MPG is also directly related to driving style, diving mode, city vs highway, etc. I am very interested in buying a 3G RDX, so I want to know everything about the car that I can - and a Big Thank You to all the current owners who take the chance on a first model year redesign and help identify problems for Acura to fix.

I think that Acura should add an ECO mode where the turbo boost profile runs less boost so that when you don't care about 272HP, you can get an easy 30+ MPG on the highway say driving across miles of straight flat highways, knowing that when you get to some twisting mountain roads you switch back to Sport+ and have a blast. It's all about improving the car in all aspects.

Notte

What is thread bombing? I'm pretty sure I just stated an opinion about the thread. RDX is much much more than mpg and its easily felt when driving it. Afterall, it has some NSX inspirations to drive home this SUV is about performance first.

ednigma

Thread Bombing is like photo bombing and basically what you did in the post I quoted. This thread was started by a new owner who wanted to know the actual MPG other owners were getting. In other words, facts. Facts which are of interest to many owners and prospective owners. You post that we should stop all this talk about MPG because if you buy an RDX you should not care about MPG. Your opinion is that this thread is a waste of time, instead we should be talking about how much fun it is to drive. Okay, you don't care so much about MPG, that's fine, but you see a thread titled "Post Actual MPG On Your New RDX" and instead of skipping the thread you specifically make a sarcastic post that the thread should be about something else. Like another poster suggested, you should start a thread about how much fun it is to drive, that way people who want to talk about the driving feel of the RDX can follow that and comment. You know, freedom of choice.

My apologies to the rest of the posters for adding to the noise level.

Stew4HD

Thread bombing is very common on forums. Someone creates a thread about how they like something such as Expresso color interior. and others feel compelled to express that the think the color looks like baby crap... such is forum life

TxLady

geocord

MI-RDX

Stew4HD

I am seeing a 70 cent difference here in my area. What happened to the 20 cent diff?

TLMDXRDX

Not sure if you guys have a Thornton's near you, but I have found they have the smallest differential between 87 octane and their premium (91 octane), and that difference if consistently 40 cents. If you get a free rewards card you also automatically get 3 cents off per gallon and I usually get a weekly email to double that to 6 cents off a gallon.

As for my new RDX, I have 300 miles on it so far with about half on the highway and have in city and I am getting 21.0 MPG and that is not with my usual more aggressive driving. I know there is a break in period so I am hoping it will go up a bit more.

ednigma

Costco in my area, the difference is also about $0.60, but its between 87 and 93 octane. I don't think I've seen a car (non exotic or special hi perf engine) require 93 octane. My summer car, a 97 BMW M3 with aftermarket engine program only specifies 91 octane minimum. Maybe the difference would be less for 91 octane. Then again the nearby Kroger sells a midgrade 89 octane, so mixing 93 and 87 might be simpler

Fury63

TLMDXRDX

So I have had my new RDX for about a month and just went over the 1000 mile mark today and I have averaged 19.7 MPG with about 75% city driving and 25% highway driving in comfort mode all but a couple times. I have to say I was hoping for near 21 mpgs with this ratio. I reset my trip meter on a drive out of town this afternoon and had to drive in a construction zone going 55 and that is the only time I have seen the MPGs cross 26. When I was out of the construction zone and went another 30 miles at 75 to 77 mph the average dropped to about 22.4. It seems the only way to get the true highway miles is to go between 45 and 55 mph which is not too realistic for most US highways.

Is anyone else getting better MPG with highway or city driving? I am not gunning it really and have probably driven more calmly than usual.

Fury63

TLMDXRDX

Yes comfort mode and premium fuel, and on flat Illinois roads with no elevation.

MTD

RDX A-Spec here, Ive got about 4000kms (2500 miles) about 75/25 city/hwy and Im averaging about 24 mpg in sport mode and premium fuel. 55mph may be unrealistically slow to drive, but isnt that the speed that a vehicles fuel economy is tested at?