Mazda 6 Forums banner
1 - 9 of 9 Posts

·
Registered
Joined
·
3,592 Posts
Fuel blends are seasonal and can have a quite-material impact on mileage. In addition warm-up times as noted are longer and until the ECU goes into closed-loop operation (when the catalyst lights off) mileage will SUCK. Short trip driving in cold weather can murder your average fuel economy between these factors.
 

·
Registered
Joined
·
3,592 Posts
10mpg is a 20-25% decline.

Something's wrong with the vehicle; I'd check for a drag sources (e.g. a dragging brake caliper) for starters.

My last 4 tanks have been down a few mpg but I've had a bike carrier on the back with bikes on it -- and that hits me for ~3-4mpg at 75mph. Drag matters, especially at highway speeds!
 

·
Registered
Joined
·
3,592 Posts
Pick the rear wheels up one at a time (jack time!); if you have a dragging caliper it will be instantly obvious when you attempt to rotate the tire manually. Fronts are trickier because normal driveline drag makes it difficult to discern the difference. This is part of my regular inspection when I rotate my tires with oil changes.

I've got nearly 20k miles on my 2015 Sport manual and my "best ever" tank was a few kilomiles back (just over 41mpg actual, measured by miles covered divided by fill volume.) I run 87 almost all the time since I tested 93; premium fuel returned a bit less mileage although IMHO the engine ran a bit smoother with more throttle responsiveness in the light throttle and lower-midrange area. IMHO not worth the materially higher cost for daily driving.

With the bike rack on back cruising @ 75-80mph I lose quite a bit over the same load but "clean" aerodynamically (e.g. bike in the TRUNK instead of on a rack) -- we're talking going from ~35 -> 30ish over the same road and comparable conditions. That's a huge change and yet the bike and rack are both in the slipsteam (hitch-mounted platform rack; nothing extends beyond the profile of the vehicle) so don't ever believe that minor drag changes will not murder your mileage, especially on the highway, because it does.
 

·
Registered
Joined
·
3,592 Posts
bump,

I'm not far into the first fill after the additive, but so far performance hasn't dropped from the tank WITH the additive, and MPG is up back around 34MPG average so far this tank. That's a near 5MPG (re)gain indicated so far.. but I'm only 100 miles in, so we shall see
If this holds up, it's safe to say the valve timing definitely allows for valve cleaning, and a little boost every now and then with something like the techron/seafoam/etc wouldn't be a bad idea. For this to be effective, fuel must get to the top side of the valve, thus the concern of it not working at all on a DI engine.
No it's not.

It's equally (in fact more) likely you had one or more partially-fouled injectors and the extreme detergent level of what you ran through them restored a reasonable spray pattern.
I'll be opting for a full top-end cleaning and media blasting of the valves at 50K (BMW regular maint.) if I still have this car at that point.
I would certainly inspect before undertaking such an operation.
 

·
Registered
Joined
·
3,592 Posts
I have ~22k on my car, have run no additives in the fuel (or anywhere else) and have no noted degradation (or any other change for that matter) in the mpg pattern or engine operation.

I do tend to run top-tier fuel when home, favoring Exxon and Shell stations (both of which are convenient to my usual stomping grounds and competitive in price.) The exception is on trips where I usually favor the high-volume stations (e.g. truck stops such as Love's, etc.)
 

·
Registered
Joined
·
3,592 Posts
I've got almost 23,000 miles on my "6" since March (of this year!) and outside of a couple of small dings in the paint (mainly on the plastics in the front, not on the metal itself) consistent with various minor road debris it runs, rides and looks like it did the day I got it. Brake and tire wear are right "up the middle."

IMHO the "6" is an incredible road car. I've had a lot of vehicles over my years and in terms of overall driving experience for long periods of time behind the wheel I've not owned anything else I'd prefer. There are many faster and more-complex vehicles to choose from but in terms of the total driving experience it's a matter of balance -- IMHO Mazda has done a great job in that regard.
 

·
Registered
Joined
·
3,592 Posts
I honestly don't get jon2002. He comes in with a holier-than-thou attitude because he thinks his cheap ass is superior because he pumps lower quality gas. I feel dumber just typing it out. And on top of it, he is super condescending.
There is no difference in the QUALITY of the gas between premium and regular. It is simply the octane rating. This has been repeatedly demonstrated by testing on "regular" and "premium" from various top tier gas companies; the additive package is identical in both.

Higher octane fuel burns slower, all things being equal. You run higher octane because your engine can take advantage of it (or is set up to REQUIRE it and will detonate if you don't use it.) The SkyActiv engine does not require it; the US version has been specifically detuned in its maximum compression ratio.

The "6" is known to return slightly lower mileage on premium (which is expected behavior if an engine does not require premium fuel as it does not have the higher C/R that is necessary to take advantage of it.) The reason for this is that an engine's efficiency would be at it's highest if the fuel was to burn instantaneously at the point of maximum compression, which provides the highest expansion ratio. This is physically impossible but the closer you get without detonation the more efficient the engine is. As a result if you do not need the higher octane to avoid detonation the car will return slightly less fuel economy on premium.

However, on premium the "6" is a bit smoother in operation under light throttle acceleration at lower RPMs. This is probably due to running into the knock sensor under those conditions in the ECU's maps (it's a prime place for knocking to occur in modern engine designs) on regular fuel; if you find that annoying enough to spend the money then that's what you should do.

In terms of benefit (e.g. better service life, less injector/combustion chamber fouling, etc) there is none if you're buying quality fuel in the first place.
 

·
Registered
Joined
·
3,592 Posts
I don't know what's going on with your car but mine now has about 34k miles on it and mileage has actually gone up a fair bit -- with an OVT tune on it. :)

Not just a little either -- about 3-4mpg @ 75mph, which for the MTX takes it out of the "atkinson" mode stock and thus results in a ~33ish MPG reading (it's close to 40 mpg @ 62-63ish!) With the tune, however, that's addressed and the result is right around 37 on long trips with the cruise locked.

The car is bone stock otherwise; I've also run a number of oil analysis on it and there's nothing to indicate any sort of material internal wear is occurring. If the pattern I've established now holds I expect to easily reach 200k miles.

http://www.fuelly.com/car/mazda/6/2015/tickerguy/279156
 
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top