"Help! How can I get better mileage?"
 

Hi Guys,

This is the thread that belongs to all SVX members who are getting low mileage. This posting idea is of UberRoo.

Here please post replies on how to get better gas mileage and to improve the efficiency of gas. Any suggestions and advices are needed from those who get better and high mileage and help low mileage (including me) svx members to boost their gas efficiency atleast to acceptable levels.

thanks,
Pavan.:)

Get new O2 sensors.

ECUtune stage 1, You can then run 87 octane.

New O2 sensors
 

I second that.

My 92 with 92,XXX miles was averaging a consistent 20 - 21 MPG on a 80% hwy/20% city driving cycle. I had no CEL's, but replaced the O2 sensors with new ones. It was obvious the old ones were original. At the same time, I replaced the main cat with a high flow Magnaflow and also installed an ECUtune v.4 chip. The end result was a gain in MPG to a conmsistenmt 24 with the same driving style and hwy/city mix. On extended hwy rides, I average 27 MPG.

I have a 5 speed with the 3.90 rear end so I don't think I'll ever see 28 or 29 MPG like some members have on the boards, but I'm pretty pleased with 24 MPG.

Keep in mind that as O2 sensor performance degrades over time, the default condition of any ECU is to run rich to prevent detonation which often shows up as decreased gas mileage and sooty tailpipes. You don't have to spend a fortune either. I bought Walker direct fit replacements for around $64 each from www.oxygensensors.com (factory Denso sensors are around $94 ea.). If you feel confident of your soldering skills, you can buy Walker universals for around $40 ea, but you have to solder and terminate the ends of the wires yourself.

Last week's 625+ mile trip through Seattle...
 

...I averaged almost 28 mpg. I suggest a cruise control set @ 80 helps on longer trips. Maintaining your SVX (plugs, timing belt, fuel filter, air filter, the DREADED PCV, any and all electronic engine controls) to spec certainly helps mpg. BTW, I use mid-grade gas almost exclusively, now.

But, in the final chapter, it REALLY all is centered about your right foot in non-freeway situations: fast starts and the need to apply the brakes really tears up the stop & go gas mileage. TWENTY is GOOD! if you are rip-roaring about town, IMHO!

My O2 sensors are original and I don't think I have ever had an engine light code appear in 12+ years and 121+K miles.

Knock wood! & CHEERS!

Norm

The rated capacity of our tanks is 18.5 gallons. I've been keeping a gas can in the trunk and running my tank empty. After pouring in the contents of the gas can (1.8 gallons), I can usually squeeze another 17 gallons into my tank. I run out at about 300 miles. That's about 16 MPG. Grrr... The rated mileage is supposed to be 17 city, 24 highway.

MPG = Miles Per Tank @ 18.5 Gallons (@ 16 Gallons)
--------------------------------------------------
10.0 = 185 (160)
10.5 = 194 (168)
11.0 = 204 (176)
11.5 = 213 (184)
12.0 = 222 (192)
12.5 = 231 (200)
13.0 = 241 (208)
13.5 = 250 (216)
14.0 = 259 (224)
14.5 = 268 (232)
15.0 = 278 (240)
15.5 = 287 (248)
16.0 = 296 (256)
16.5 = 305 (264)
17.0 = 315 (272)
17.5 = 324 (280)
18.0 = 333 (288)
18.5 = 342 (296)
19.0 = 352 (304)
19.5 = 360 (312)
20.0 = 370 (320)
20.5 = 379 (328)
21.0 = 389 (336)
21.5 = 398 (344)
22.0 = 407 (352)
22.5 = 416 (360)
23.0 = 426 (368)
23.5 = 435 (376)
24.0 = 444 (384)
24.5 = 453 (392)
25.0 = 463 (400)
25.5 = 472 (408)
26.0 = 481 (416)
26.5 = 490 (424)
27.0 = 500 (432)

I included miles per tank at 16 gallons because I figure that's when most people fill up again. Notice that near the end of this scale, running the tank dry lets you go another 50 miles.

Still, at 10,000 miles per year, the difference between 16MPG and 20MPG only adds up to 125 gallons. At $2 per gallon, that's $250. Probably not worth the expense of having a shop investigate. That's about the cost of new oxygen sensors, a set of spark plugs, an air filter, and a fuel filter. If you have a shop do the work, you can stack labour on top of that.

I've heard some people say that replacing the O2 sensors can perform miracles. I've heard other people say rubbish to the whole notion. Both sides have a reasonably strong argument, so I figure it's not a black and white issue, and worth considering once the other [cheaper, easier] options are exhausted.

Has anyone seen any conclusive evidence that the EGR valve significantly affects fuel economy? I haven't really looked into it, but I could certainly see the potential. I'm pretty sure it's rather exclusively an emissions device, but no doubt it's presence is reflected in the design of other engine systems.

...still miffed that mileage would get so bad so suddenly without turing the CE light on...

I've been checking mileage at every fill-up for the last few months and have been getting a consistent 16 - 16.5 mpg with 80% city driving. I usually use around 16.5 gallons before i fill up. I changed my PCV valve a few days ago and the one that i took out was definately not working. It was plugged up with sticky black stuff and the little thing inside it wasnt even moving. So I put the new one in and im hoping for an increase in mileage. If it works I will let you all know.

:)
-Evan

want to save gas? take the bus....;) seriously if mileage is a big issue..one should not drive an SVX...heavy car..awd...big engine...its not a Geo Metro..cant expect miracles...now the RX-7's ive owned got horrible gas mileage...and didnt perform too well for such bad mileage..my SVX gets about 23-25mpg average and I drive 'spirted'..my Probe got about the same and performed less..it balances out for me

Hi Weasel 22,

we are not worried for bad gas mileage, but rather we are concerned about the engine. Bad mileage = Something wrong with the engine (Hoping the average driving conditions). So we want to rectify those engine defects by taking advices from other members getting high mileage.

Anyway your idea of takin a bus is wonderful and great.... ;) ;) :D .

Pavan.

after drinking more coffee im seeing what the subject was about...yes tuning the engine to better levels is ideal..I have many friends who constantly complain about their cars mileage..which puts me at the Geo Metro thing..buy the car for your needs..if you are getting terrible mileage from your SVX and know it can do better, I fully agree on the tune up :D :D

Once you get past the basic pieces - plugs, air filter, keeping the tires correctly inflated, 4 wheel alignment- you'll also want to make sure the TB is clean (make sure to use Fuel Injector spray, not carb cleaner), the MAF is operating correctly, the Cats (all three of them!!) aren't clogged up with age (thus restricting exhaust flow), all of the various vacuum lines are intact - and not cracked due to age, thus creating vacuum leaks, the PCV valve is operating correctly, and the O2 sensors are functioning correctly.
What I'm finding is that a lot of the various lines - emissions, vacuum, electrical have seriously gone brittle on my SVX after 13 years and 186k miles!:eek:
-Bill

So that gallon of toluene seems to be doing something. It doesn't feel faster. The fuel gauge seems to be dropping at the same rate. My check engine light still comes on sometimes and leaves EGR and temperature sensor codes. But... I've found myself looking down at the speedometer only to discover I'm going a little more than ten miles per hour faster than I was expecting. It doesn't seem to make any difference around town, but I think I may be getting quite a bit more top-end. ...that or the placebo effect is amazing.

Normally I go up certain hills on my commute at about 65 with the torque converter locked up. It unlocks if I go much faster. I've found myself above 80 three times now with the torque converter locked up and I didn't even notice until I started wondering why traffic around me seemed to be moving so slowly.

Driveability so far is otherwise unaffected. It'll be at least another week before I can check for any fuel economy changes.

So wait a second....i usually fill up at the quarter tank mark...how much is left in the tank when it gets to that point? I usually get 165 miles up to that mark. City driving with a tiny bit of highway.

In theory, at 165 miles you should have another eight or nine gallons left, but in reality it's probably not quite that much. We all should be able to go 300 miles on a tank, but I guess we don't all make it that far.

I don't even think about filling up until I get the low fuel warning light. I don't pay any attention to the gauge because it's so far off. When I see 275 miles, I start looking around for an oil station.

The real key is how many gallons you put in at the pump. I make sure that mine always sucks down at least sixteen gallons.

Isn't that bad for the fuel pump if you let the gas get low to the point that the light stays on? Doesnt it let dirt get in? Thats why ive always been filling up at the quarter tank mark. If i let it get low enough for the light i could definitley get at least 250 out of it.