Mazda 6 Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
790 Posts
Discussion Starter #1
Took the Wife to the Vegas Airport so she could fly out and see our Daughter for a week who lives in S. Dakota. We live 120 miles N of Vegas so 240 miles round trip. Turned 1K miles on the ODO on the way there.

Thought this would be a good stretch on the way back to get a good idea of the highway mpg so filled up after leaving the Vegas Airport, reset the odo and drove the 120 miles back home which is all Interstate (I-15) and was pleasantly surprised to average 33.7 mpg.

This was staying with the flow of traffic which was between 80 and 85 mph. Had a few stretches where 90 was the norm. Road is reasonably flat with a bit of a climb the last 20+ miles. Also had a 10-15 mph headwind about half the time.

The car was running 89 octane so I would assume mileage would have been slightly better with 91 (we don't have 93 around here). I'd also bet if you kept the speed around 65-70 you could hit 35 mpg fairly easy. Pretty good for a car rated at 31 highway. I'd also say it seems that with each tank as the engine has broke in the mileage and performance seem to have improved.

Seemed as though the engine never even broke a sweat. Plenty of power on reserve for some quick bursts when passing. Jumped quickly and willingly from 80 to 100 when needing to pass. Like most folks are saying, this engine is a sleeper. It will get up and run.

Summing this up, a mid-sized 4 door Sport Sedan with 250 HP (premium gas) achieving close to 35 mpg around 65-70 mph on the Interstate is pretty darn good. That type of performance and economy rates it right near the top in the SPG department. (Smiles Per Gallon) :smile2:
 

·
Registered
Joined
·
55 Posts
lucky!im averaging 22 spg and when fill up my whole tank it says around 315 mile range,you mind me asking what yours says?only usimg 91 octane since like you said no 93 here in vegas
 

·
Administrator
Joined
·
8,494 Posts
If it's like any other Mazda engine, the mileage will only get better as it gets "worn in".

It's interesting to see how mileage will be affected by the octane. Conventional Wisdom says that it'll probably improve with higher octane, but I've also seen different cars/engines where it stay the same, or even drop as much as 4-5 MPG...
 

·
Registered
Joined
·
790 Posts
Discussion Starter #4
lucky!im averaging 22 spg and when fill up my whole tank it says around 315 mile range,you mind me asking what yours says?only usimg 91 octane since like you said no 93 here in vegas
Up to this point most of the driving has been city and the mpg have not been anywhere near as good as the highway mpg I got yesterday. I'll pay closer to attention what it says next time when I fill. IF I remember it was more like 405? If you're not used to driving a Turbocharged motor, when the turbo(s) kick in (start spooling) your mpg drop considerably. Trying to stay out of boost makes a big difference in your mpg.

If it's like any other Mazda engine, the mileage will only get better as it gets "worn in".

It's interesting to see how mileage will be affected by the octane. Conventional Wisdom says that it'll probably improve with higher octane, but I've also seen different cars/engines where it stay the same, or even drop as much as 4-5 MPG...
With the HP improving with higher octane I would think the mileage should increase as well.

You have to pay attention to the pumps this time of year around here as we switch from winter to summer blend. Some of the "regular" gas can be 85 octane. "mid" grade is 88 and premium 91. I tell the wife not to fill up, I'll do it. Once we get the winter gas gone I'll start experimenting a little to see how the different octanes affect mileage.
 

·
Registered
Joined
·
45 Posts
lucky!im averaging 22 spg and when fill up my whole tank it says around 315 mile range,you mind me asking what yours says?only usimg 91 octane since like you said no 93 here in vegas
Mind you though the tank is not the size Mazda say it is. The figures say it is 62 lt. I have had three 6's, to stationwagons and a saloon. Even if the gauge says you have just two km left, you can not fill it with more than 54 lt. Either you can go a long way beyond what it says is the range, or the tank is smaller. As mine have all been diesels that do not like running dry, I have not taken any chances. It is about the only thing that annoys me with the car. The difference between the official size and the apparent actual size is about 160 KM per tank. When I fill mine up the car says that I have a range of about 950 Km which fits with the electonic's kilometer per 100km value X 52. So the car also thinks the tank is smaller the the specification says.
 

·
Registered
Joined
·
3,054 Posts
There are two issues with regard to tank size.

For GAS engine vehicles there MUST be some space remaining in the tank OR the charcoal canister will flood, destroying it. That's quite-expensive to replace and since it's emissions-related in the US anyway there's a federally-mandated 80,000 mile warranty on it, which means the manufacturer eats it. As a result on a gas engine vehicle the tank vent is strategically located so as to prevent filling the tank all the way, trapping a nice big air bubble in it to protect the canister. This of course impacts miles-to-empty in a material way; in MOST vehicles it's good for at least two full gallons of capacity!

On DIESELS there's no need for this since there's no charcoal canister. There you need only expansion room in the event the fuel gets (very) hot compared against what it is in the station's storage tank. No big deal, and if you drive a couple of miles home from the station there's more than enough room.

BUT, since manufacturers hate making two assemblies where one will do, they usually use the same tank and vent design. On VWs at least you can fairly-easily remove the "guts" of the vent assembly from the filler neck and regain the 2+ gallons of capacity if you own a diesel.

It is a very bad idea to do this if you have a gas-powered car, however, as a flooded charcoal canister will likely be detected by the ECU when it does its negative/positive pressure check during normal operation and will set a code (and the MIL.)
 

·
Registered
Joined
·
790 Posts
Discussion Starter #7
There are two issues with regard to tank size.

For GAS engine vehicles there MUST be some space remaining in the tank OR the charcoal canister will flood, destroying it.
Not trying to pick on the Costco gas users but If you use Costco to get gas have ever noticed how many people sit there and squeeze every drop they can into the gas tank until it starts running down the side of the fender? This is with the "Don't top off" sign right next to them.

And then they wonder why their check engine light is on (flooded canister).... :surprise:
 

·
Registered
Joined
·
55 Posts
There are two issues with regard to tank size.

For GAS engine vehicles there MUST be some space remaining in the tank OR the charcoal canister will flood, destroying it. That's quite-expensive to replace and since it's emissions-related in the US anyway there's a federally-mandated 80,000 mile warranty on it, which means the manufacturer eats it. As a result on a gas engine vehicle the tank vent is strategically located so as to prevent filling the tank all the way, trapping a nice big air bubble in it to protect the canister. This of course impacts miles-to-empty in a material way; in MOST vehicles it's good for at least two full gallons of capacity!

On DIESELS there's no need for this since there's no charcoal canister. There you need only expansion room in the event the fuel gets (very) hot compared against what it is in the station's storage tank. No big deal, and if you drive a couple of miles home from the station there's more than enough room.

BUT, since manufacturers hate making two assemblies where one will do, they usually use the same tank and vent design. On VWs at least you can fairly-easily remove the "guts" of the vent assembly from the filler neck and regain the 2+ gallons of capacity if you own a diesel.

It is a very bad idea to do this if you have a gas-powered car, however, as a flooded charcoal canister will likely be detected by the ECU when it does its negative/positive pressure check during normal operation and will set a code (and the MIL.)
thanks for the explanation!I wondered why with even 8 miles remaining till empty I was only able to put a little over 13 gallons,thoight maybe I had gotten a bad tank or somthing was inside the tank but now i know lol
 

·
Registered
Joined
·
5 Posts
Mind you though the tank is not the size Mazda say it is. The figures say it is 62 lt. I have had three 6's, to stationwagons and a saloon. Even if the gauge says you have just two km left, you can not fill it with more than 54 lt. Either you can go a long way beyond what it says is the range, or the tank is smaller. As mine have all been diesels that do not like running dry, I have not taken any chances. It is about the only thing that annoys me with the car. The difference between the official size and the apparent actual size is about 160 KM per tank. When I fill mine up the car says that I have a range of about 950 Km which fits with the electonic's kilometer per 100km value X 52. So the car also thinks the tank is smaller the the specification says.
They're not selling cars with gas tanks smaller than specified. Instead, they've got the car's computer lying to you about how much distance you've got left. Doing it that way causes fewer problems than if the car's computer told customers the truth.

They'd much rather have you driving around with more fuel than you realize than have you run out of fuel or have the fuel pump dredge up crap from the bottom of the tank. If those things happen, people will blame them for it, tell their friends, etc. Far better for them to ensure you've got more fuel than the car's computer tells you about.

My bride's Acura hides about 2 gallons of fuel from her. I don't know how much fuel cushion is typical, but I bet having one is normal.
 

·
Registered
Joined
·
5 Posts
There are two issues with regard to tank size.

For GAS engine vehicles there MUST be some space remaining in the tank OR the charcoal canister will flood, destroying it. That's quite-expensive to replace and since it's emissions-related in the US anyway there's a federally-mandated 80,000 mile warranty on it, which means the manufacturer eats it. As a result on a gas engine vehicle the tank vent is strategically located so as to prevent filling the tank all the way, trapping a nice big air bubble in it to protect the canister. This of course impacts miles-to-empty in a material way; in MOST vehicles it's good for at least two full gallons of capacity!

On DIESELS there's no need for this since there's no charcoal canister. There you need only expansion room in the event the fuel gets (very) hot compared against what it is in the station's storage tank. No big deal, and if you drive a couple of miles home from the station there's more than enough room.

BUT, since manufacturers hate making two assemblies where one will do, they usually use the same tank and vent design. On VWs at least you can fairly-easily remove the "guts" of the vent assembly from the filler neck and regain the 2+ gallons of capacity if you own a diesel.

It is a very bad idea to do this if you have a gas-powered car, however, as a flooded charcoal canister will likely be detected by the ECU when it does its negative/positive pressure check during normal operation and will set a code (and the MIL.)
Thanks for that... you taught me something...
 

·
Registered
Joined
·
104 Posts
Lumping in this motor with the other newer forms of direct injection, your oil weight will also cause fluctuations in fuel economy. As oiling passages have shrunken the past 20 years with the evolution of casting technologies, and tolerances of reciprocating components continues to shrink and shear protection goes up, oil weight is now has a much more direct impact on fuel economy than ever before.

There have been many cases of specific motors grenading due to oil starvation as owners put 10w40 into motors requiring 0w30 or even 0w20. Looking at you, Toyota, and your silly hybrids!

On my built 1938 flathead, you need 20w50 or the top of the block physically won't receive oiling. The oil is like syrup!

Where the argument always goes sideways is the topic of synthetic vs. non-synthetic. Personally, even if the car can take synthetic, during the break-in of the motor, i'll be using OEM suggested weight non-synthetic oils. Then switch to synthetics after about 6k miles of hard driving. the super-slick nature of synthetics has been discussed at length all over the world and such places as BobIsTheOilGuy, it seems to be, and from oil samples sent to blackstone labs, that the non-synthetics would allow slightly greater wear/friction which is beneficial to motor break-in.

Not sure how the high-zinc formulas will stack up on the 2.5T, but they were a must-have on the dual scroll turbos that Evo's had been turning to, and also in the high-friction classic motors. The plan is to test a few oils with 5K service intervals and submit samples to blackstone to see how they are really performing in this engine... Results to follow over the coming years!
 
1 - 13 of 13 Posts
Top