Amazing Bidness Economy, an MPG Parable...

[7milesout]

Guys,

I just had to take a quick run out of town on bidness. A last minute, "hey go check this" kind of thing.

I had to go to SPARTA-nburg, SC. Great place. That whole Greenville to Spartanburg region. Great people, great area, very unAtlanta. No skunky smell of "diversity" everywhere you go, like in Atlanta. Anywho...

I had about 75 miles on the tank already and took off to Spartanburg Tuesday evening, after the Atlanta road wars on the Watermelon 500 had mostly subsided. And cruised my way on up there. No A/C, just put the windows down. Was very comfortable.

It's just under 200 miles to there. Then Wednesday (yesterday) I decided to juice it up on my way out of town. I got 45.952 mpg on that tank to get up there. I left there about 1 pm, and it was quite warm. So I decided I would do an all-interstate cruise with the A/C on and refill it near my house just to see what the cute little bad-ass tow rig Blueberry would do with the A/C on.

It got 48.7 mpg on the way back, with the A/C on. That's to the first click off of the fuel pump. In reality, I'm going to bet it was in the 47's for true mpg. But in any event, I was AMAZED at the interstate mpg.


Here's what I did different than I had ever done before. This forum has clarified that at ~3,500 rpm is where the (big time) MIVEC system starts MIVEC'ing. As I understand, it is just intake-side valve timing. I don't know if it opens sooner, opens later, or both. So I slapped in my ELM 327 and ran the (free) torque light app, and set my Cruise control at 3,475 rpm. That's just barely skimming 69 mph. I did this both on the way there and on the way back.

Watching the app, the rpm would run 3,475 ± 75 rpm or so. So yes, it would run up and into 3,500 rpm. However, when it would run into the 3,500+ rpm zone, it would back off the throttle in order to try to achieve the set speed at 3,475 rpm. So even if it MIVEC'd even a skosh over 3,500 rpm, it was off-throttle MIVECing. So I summized MIVEC was having little to no negative effect on mpg in those off-throttle 3,500+ rpm events.

I guess this is applicable to mainly the 5-speed guys. As I would imagine the rpm would be all over the place with a CVT. Especially on this run. That run down from Greenville back to the GA state line was very much UP-DOWN-UP-DOWN-UP-DOWN. Same in GA, just less steep and less compressed with the up-downs.

On the speedometer, let me explain where to set the cruise (if anyone is interested ... (crickets, crickets, crickets)). If you can exactly center the gauge on the 70 mph mark, and then juuuuust barely skew it off ever so slightly off-center of that 70 mph mark to the right, and set it there ... that's where it was on my guage hitting 3,475 rpm through the app. I'm going to guess that numbers on the app were more accurate than the tachometer. I didn't pay much attention to the tachometer. It was close to the same rpm anyway.

Many have said, the Mirage is not a good interstate car. I do see their point. However, if you can sit comfortably in the car, and have the discipline to roll along at 69 mph, set the tach as described above, run the A/C as necessary, and KNOCK OUT some especially good fuel economy! Ohio and Kentucky used to have maximum speeds of 65 mph (don't know what it is today). And SC had a max speed of 65 mph where I was. So 69 mph wasn't too far behind the average, and was quite a comfortable cruise.

[foama]

Mine is an 1.0L/3A90 with a slightly taller European MT. If I take my time in the countryside it will use about 3.9L/100km. That might be about 60mpg/US.
BTW family lives in Greenville, and a few more in Atlanta.

[7milesout]

Your family in Greenville ... are they BMW employees? Or BMW tier 1 / tier 2 supplier employees?

I feel bad for your Atlanta relatives. They must paint a dim picture of the USA. Atlanta is a skunk-ass smelly diversity horror story.

And I (and most on here) are jealous of your 3A90. The Euro gearing ... is probably more advantageous than not.

[Mark]

I try to stay within 5 mph of the speed limit. I like to keep my driving record clean for my driving instructor license, my class A CDL, & my car insurance premium. I feel within 5 mph is somewhat safe.

My parents live approximately 215 miles from my house, & I do that drive with my Mirage quite often. 125 miles of that is 2-lanes/55 mph highways, and the remaining 90 miles are 4-lanes/70 mph highways.

I would agree that the 5-speed manual does quite well under 70 mph. I see the most noticeable drop in economy @ 75+ mph. My economy light starts to disappear when it gets near 80 mph. I see that in North Dakota, which has 75 mph highways & push it to 80 mph sometimes.

The taller European 5th gear would be nice. For my daily driving around where I live, the car is perfectly fine as is.

I canned the wheel covers recently. I had a mix of 2014-15 & 2017+ wheel covers. I found the older wheel covers don't fit tight. I think they make some rattling noise, too. They surely don't stay on very well, and I am not going to zip tie them on. The newer ones fit much tighter, but that causes them to break more easily. I'm just tired of dealing with them. It's black steel rims for now, and I am not painting them either. It's an economy car, & I don't care about the look of my wheels all that much.

I bring that up, because I don't think it impacted fuel economy at all. If anything it seems slightly better since I've taken them off, but summer fuel/tires make things better, too.

[7milesout]

It's black steel rims for now, and I am not painting them either. It's an economy car, & I don't care about the look of my wheels all that much.

I bring that up, because I don't think it impacted fuel economy at all. If anything it seems slightly better since I've taken them off, but summer fuel/tires make things better, too.

Don't be such a Yokohama Mama, and black paint them suckers brother! Then we can both be smoooooth rollin'.

I don't think the wheel covers gave any mpg benefit either. Mine has been the same if not a skosh better without them.

And now, mine can blow off all that extreme heat a lot mo' bettuh without the insulators hats on, from all the times I hit my break marker down at the end of the back stretch at Road Atlanta.

[Mark]

Don't be such a Yokohama Mama, and black paint them suckers brother! Then we can both be smoooooth rollin'.

I don't think the wheel covers gave any mpg benefit either. Mine has been the same if not a skosh better without them.

And now, mine can blow off all that extreme heat a lot mo' bettuh without the insulators hats on, from all the times I hit my break marker down at the end of the back stretch at Road Atlanta.

I drove in the rain today. They look cleaner than yesterday.

I have 8 black steel rims (4 factory, 2 from Dirk, and 2 aftermarket ones) for my Mirage.

You can park next to me, & everyone can admire your wheels over mine.

[MetroMPG]

I don't think the wheel covers gave any mpg benefit either.

I would bet you a Tim Hortons Timbit that they do! Wheel drag is one of the biggest contributors & easiest "fixes" to lower overall aero drag.

The difference is just too small to see in the normal noise of tank-to-tank results.

[7milesout]

Yeah, but my wheels are painted black, and that paint is SLICK. So ... there's that.

[Wallythacker]

Read the specs on our engines. Max torque is produced at 4k. 100 ft. lbs. I feel the max torque is closer to 3600. my 1986 2.3 l Tempo had 124 ft. lb. of torque and I towed 2000 lb. regularly.
The ECO light goes out @>3600rpm

So just before the computer recognizes wind resistance and increased fuel consumption our engines are producing nearly their maximum muscle. This is the ideal situation, a hill appears, who cares the engine will handle it, a moderate gusty headwind, who cares, the engine will handle it. Got a trailer? Well, that's the best rpm for pulling stuff.

My best mpg has been at 40-50mph night drives, I managed about 75mpg IRRC with snow tires. Prettygoodn

[inuvik]

I would bet you a Tim Hortons Timbit that they do! Wheel drag is one of the biggest contributors & easiest "fixes" to lower overall aero drag.

The difference is just too small to see in the normal noise of tank-to-tank results.

I agree, those big full size "moon disc" wheel covers will improved mpg's. There is a lot of drag associated with air flow turbulence within the wheel itself depending on design.