Higher speed not as bad as I thought

[mrmad]

I have been trying to keep the speed to around 65mph, which on I-15 north of San Diego, means I'm getting run over and pushed into the two slow lanes with the semi's, which are their own hazard.

Since getting gas at the same station for the last 5 or 6 tanks, I have managed to get my tank mileage pretty much near my average, so I'm reasonably confident in the mileage figures.

After a minor emergency at home meant I pushed the CRX home at over 85mph on one of the 45 mile legs of my commute didn't seem to effect my mileage, I thought I'd try raising the average speed from 65 to 75 to see how bad it would effect the mileage. Surprisingly, it didn't seem to effect it that much. The five tanks before this averaged 43.46, and this one was 42.50.

I'm going to try it for the next couple tanks to see if the average stays somewhere around 43. The extra speed shaves a few minutes off the commute, but more importantly, gets me out of the first two slow lanes and into the third lane where I don't have to worry about the semi's and the merging traffic.

[96hb]

Good deal. I would go ahead and raise my speed too. I mean it's less than 1 mpg. Not really worth going slower for that minute savings, IMO.

[GasSavers_rGS]

mrmad,

Your post reminded me of the famous quote from Yoda that goes "Once you start down the dark path, forever will it dominate your destiny, consume you it will..."

Source:

1. Star wars quotes, Yoda quotes, quotes from the star wars movies - http://www.some-guy.com/quotes/starwars.html

[omgwtfbyobbq]

Originally Posted by mrmad

I have been trying to keep the speed to around 65mph, which on I-15 north of San Diego, means I'm getting run over and pushed into the two slow lanes with the semi's, which are their own hazard.

That's so odd... I'll take semi drivers over all the other CA drivers any time anywhere. While they may not be as good as they used to, there's still something to say for a professional driver compared to a CA driver imo. If you find that raising your average speed by ~10-20mph only cuts off a few mpgs, it probably means that you're geared such that the increase in power needed is more or less offset by the increase in efficiency. On the downside, you can't drive slower and see significantly better mileage, but on the upside, you could probably see something like 65mpg@65mph with the proper ratio fifth. You may also be going just fast enough to pass semis instead of riding with them or getting passed by them. To pass or be passed by semis only requires a ~5mph difference in speed ime. To get a good idea of whether speed really hurts mileage, you should probably try to go for an average highway speed of 60mph versus 70mph, or some similarly large spread.

[JanGeo]

A few speed changes in the slower lanes to avoid traffic will cost you some mileage over a more steady higher speed a couple of lanes over. You also get a better draft at higher speeds from vehicles ahead of you so that can offset the greater speed losses.

[brucepick]

Yeah. You guys with aerodynamic cars maybe can do that.
I hurt myself badly a couple weeks ago when I thought I could go faster than I usually do. Pulled me down maybe 10-15% of the 30-32 mpg that I usually get.

But of course my car has all the aerodynamic features of a brick. Which is why all my optional work on it lately has been in the aero area.

[bbgobie]

I'd say my car is fairly Ok with the Aero. I notice on my scanguage when i'm going faster, and definately when I pull out from a nice draft of a truck.

That said when I'm in the right I don't brake at all, if I see a car is going to merge in a head I just let off the gas a little.

Originally Posted by brucepick

Yeah. You guys with aerodynamic cars maybe can do that.
I hurt myself badly a couple weeks ago when I thought I could go faster than I usually do. Pulled me down maybe 10-15% of the 30-32 mpg that I usually get.

But of course my car has all the aerodynamic features of a brick. Which is why all my optional work on it lately has been in the aero area.

[omgwtfbyobbq]

Originally Posted by JanGeo

A few speed changes in the slower lanes to avoid traffic will cost you some mileage over a more steady higher speed a couple of lanes over. You also get a better draft at higher speeds from vehicles ahead of you so that can offset the greater speed losses.

Not unless your tcc is so fidgety it'll unlock in a 2mph breeze.

[JanGeo]

Originally Posted by brucepick

Yeah. You guys with aerodynamic cars maybe can do that.
I hurt myself badly a couple weeks ago when I thought I could go faster than I usually do. Pulled me down maybe 10-15% of the 30-32 mpg that I usually get.

But of course my car has all the aerodynamic features of a brick. Which is why all my optional work on it lately has been in the aero area.

I don't know about that driving a Scion xB is pretty much a box but I get a laugh when I hear other xB guys getting in the high 20's and low 30's and I can go 75-80 and still get in the upper 30's and 60-65 still keeps me in the low 40's if there isn't a head wind.

[Lug_Nut]

Originally Posted by JanGeo

A few speed changes in the slower lanes to avoid traffic will cost you some mileage over a more steady higher speed a couple of lanes over. You also get a better draft at higher speeds from vehicles ahead of you so that can offset the greater speed losses.

Remaining in the right lane at (or just below) the posted max limit offers some advantages which I can't ignore.
1: Fewer speed changes than the speedup-slowdown-speedup 'slinky' effect of trying to maintain following distances in the lemming-line invariably in the center of the three lane.
The result is a steadier speed with the maximum very close to the average, versus the same average a lane over but higher maximums immediately followed by braking.
2: Usually (at least here in New England) less traffic in the far right.
On long rolling hills where one could see a mile or so ahead it is not uncommon to see 15 cars in the "fast" lane, 30 to 40 or so in the 'half fassed' lane, and but three or four in the 'slow' lane with me.
The result is more time to anticipate any of the fewer changes in speed.
3: An escape route on the immediate right. Not always, but usually. Some of the interstates in the Boston area permit driving in the breakdown/emergency lane during peak commuting hours when this advantage to the right lane is useless.
Anything going wrong in front of me in my lane can be easily avoided by a quick move towards, or even into, the empty lane to my right. The half fassed drivers not only are possibly hemmed in by traffic on each side, but their proximity to the vehicle in front of them limits sight line and time.
4: And finally the 'passivity' of selecting a slightly-less-than-the-average speed and sticking with it transfers the 'active' avoidance obligation to those approaching from behind. My "just under" the max limit mantra means I'm not doing to be rear ended since any closing rate would be but a few mph. I seldom gain distance on any of the few vehicles in the right lane, but when I do I have ample opportunity to pick up (or even slow) my pace to match the mediocre traffic to my left, select a suitable gap that may appear in that lemming line, slide into the queue, complete my pass, slide back out and resume my customary pace.

There are limitations to this technique, and each day may have different situations requiring different actions. When the posted is 65, but the slowest are going 75, there is no way in hell I'm going to drive just under 65. I'm not entirely stupid, I'll do 75.