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Gen1GT
10-25-2009, 11:18 AM
(I posted this thread in TOProtege, but I guess it's more appropriate here)

I do a fair amount of travel for work, and when I drove my Mazda6 every day, I noticed differences in fuel economy trends because I keep detailed records of my milage. Because I was driving the Mazda6 too much, I bought a 2005 Mazda3 GS Sport (hatch) with 70k on it to use strictly as a work car. I drive between 1000-1500 km/week between Hamilton and Cambridge, taking the exact same route every day, which is about 60km each way. Since I also do outside sales, I drive my car in a mix of 70% highway and 30% city throughout the week too.

I was using Shell 91 in my Mazda6 because it got me the best fuel economy with it, so I kept using it when I got the Mazda3. I had some discussions with persons about the validity of using higher octane in a car designed to not use it, so I thought I'd start experimenting with fuel economy, and what gives you the best/worst results.

I am now doing 5000km long experiments, which I think is a fair sample size to get a good result, and I feel it's fairly accurate over that distance. I use the same driving techniques every day, and I'm conscious of how I'm driving at all times to maintain that technique.

I do full throttle acceleration, short shifting at 3500 RPM. I brake late, and take corners fast to maintain momentum. I have Kumho Ecsta SPT's upsized to a 215/55/16, and I run between 35-40 PSI. The car has no cruise control, which hurts me because the throttle pedal in a Mazda3 is way too light and has no positive feedback which makes maintaining an exact speed rather difficult without looking at the speedo constantly. It's the lightest hatchback you can get, with no sunroof, no power mirrors, cloth seats, no rear spoiler etc.

My first 5000km sample was with everything stock, but using premium Shell 91. My second 5000km sample was using regular fuel (I always use Shell because of the Air Miles and test consistancy) in the tank again. I'm on my third 5000km sample, this time using Mobil 1 Synthetic 5W30 and regular fuel. For the fourth sample, I'm going to put on the Dunlop Graspic winter tires, to see if there's any change with them. Here's a breakdown of the samples I've done and will be doing, and I'll attach photos of my Excel spreadsheets as I finish them.

1. Shell 91 Premium Fuel, 5W20 non-synthetic
27.36 US MPG
8.6 L/100 KM

2. Shell Regular Fuel, 5W20 non-synthetic
26.17 US MPG
8.99 L/100 KM

3. Regular Fuel/Mobil 1 5w30 Synthetic
27.36 US MPG
8.6 L/100 KM

(future)

4. Regular Fuel/Synthetic/Dunlop Graspic 215/55/16 Winter tires

5. Regular Fuel/Mobil 1 5w20 Synthetic/Winter tires

6. Premium Shell 91 fuel/5w20 Synthetic/Winter tires

7. Premium/5w20 Synthetic/ 50 PSI Winter tires

...futures tests will involve a short ram intake, possible driving style changes et al.

http://i635.photobucket.com/albums/uu77/Gen1GT/Fueleconomychart.jpg

http://i635.photobucket.com/albums/uu77/Gen1GT/Mazda3premreg.jpg

http://i635.photobucket.com/albums/uu77/Gen1GT/Mazda3regreg.jpg

http://i635.photobucket.com/albums/uu77/Gen1GT/Mazda3regsynthetic.jpg

el_rodento
10-25-2009, 11:37 AM
Cool results. I'd be interested to see what effect the SRI has. It seems like the slight improvement in fuel economy with 91 octane doesn't save you money though. Right now regular gas is 0.981$/L and premium is 1.111$/L at a Sunoco station in Waterloo. So with your fuel economy that works out to 8.81$/100km for regular fuel and 9.55$/100km with premium.

Gen1GT
10-25-2009, 12:36 PM
Yeah, premium is more expensive even with the increased fuel economy. You can consider the extra cost as a expense for a longer range.

Gen1GT
11-06-2009, 09:48 PM
I'm just over 1500 KM with the winter tires, and I'm at 26.85 MPG...a bit of a drop so far.

aris
11-06-2009, 09:49 PM
I'm just over 1500 KM with the winter tires, and I'm at 26.85 MPG...a bit of a drop so far.

mine droped to when i put my snows:bang

r4BBiT
11-28-2009, 07:06 PM
makes sense if the tire is stickier (more friction)

Gen1GT
12-07-2009, 10:28 PM
Update:

Regular Fuel, 5W30 Synthetic and Winter tires (Dunlop Graspic)


http://i635.photobucket.com/albums/uu77/Gen1GT/Fueleconomychart.jpg

http://i635.photobucket.com/albums/uu77/Gen1GT/Mazda3regwinters.jpg

Gen1GT
12-17-2009, 12:16 PM
Not getting good results for the OW40 so far. I guess the better starting viscosity doesn't make up for the time I spend at operating temperature with the higher viscosity. If anyone can find any 0W20 synthetic around, especially Redline, please let me know.

thekid
12-18-2009, 09:28 AM
Josh, send me a PM our supplier has Redline 0w20 instock.

Woodman316
01-10-2010, 10:54 PM
I'm 10 liters per 100k in this realy cold weather mostly city.

Gen1GT
01-11-2010, 07:39 AM
The Mobil 1 0W40 isn't working out so far for me. I'm down to 25.8 US MPG. I'll be switching back to Shell 91 soon, however, so that should give me a 1 MPG increase.

Gen1GT
01-29-2010, 09:20 AM
Update:

Regular Fuel/Winter tires/Mobil 1 0W40 Synthetic
25.82 US MPG
9.11 L/100 KM

As you can see, 0W40 didn't work out. As Edwin will shortly point out, that 40 weight oil at operating temps is just way too high. I didn't think I'd lose nearly a whole mile per gallon, however. Regardless, I've got Shell 91 in the tank and I've already seen an improvement.

I'm going to boldly predict that the premium fuel will bring me back up to 26.5+ MPG.

So far, there's really been no suprises. Some people think there are too many variables for this experiment to valid, but the results have been along the lines of reasoning so far...

http://i635.photobucket.com/albums/uu77/Gen1GT/Fueleconomychart.jpg

http://i635.photobucket.com/albums/uu77/Gen1GT/Mazda3regwinters0w40.jpg