Saturn Math

Topic: Saturn Math (Read 1609 times) previous topic - next topic

Saturn Math

June 19, 2009, 05:38:24 PM

Hokay, here's why I like Saturns for daily drivers:

When I first bought the car a few days ago the gas gauge was showing a needle's width above empty. I reset the odometer, put $35 worth of gas in, and brought the oil up exactly to the "full" line.

Gas was $1.04 per liter when I bought it (it's at $1.10 now).

$35 worth of gas at $1.04 per liter bought me 33.65 liters.

There are about 3.8 liters per US gallon, so that works out to 8.89 gallons.

When I got home today the needle was back at the exact same position it was before I bought gas. I know this is not scientific, as there could be several liters in the difference, but it gives me a ballpark figure. The odometer read 525 km, which works out to 326 miles.

8.86 gallons to drive 326 miles works out to 36.67 MPG. This is with the A/C going the whole time, and a mixture of about 80% highway, 20% city driving. Of course, since I'm going by gauge reading over only one tank there is margin for error, but it'd only be by 1 or 2 MPG (and could either increase my figure or decrease it). That's not too frickin' shabby.

It sounds even better when I say it in terms of imperial miles per gallon, because imperial gallons are about 20% bigger than US gallons. An imperial gallon is 4.5 liters. Car companies in Canada advertise their MPG figures in imperial gallons, so we see out-to-lunch figures advertised here (such as 45MPG for Civics and Cobalts, and 30 MPG for F150's).

When doing the math using imperial gallons, my 33.65 liters works out to 7.47 imperial gallons. Using 7.47 gallons to travel 326 miles, my wileage works out to 43.64 MPG. That's not too frickin' shabby either.

This is a 12 year old car that cost me $1200 and has 172,000 miles on it (just over 276,000 km). And to make things even better, the oil hasn't gone down a drop.

Prius what?

Saturn Math

Reply #1 – June 19, 2009, 08:58:42 PM

Yes, there is no point to buy a Hybrid unless you go all out electric with it - then you have battery replacement costs. This is the one thing that Saturn did well but as we know, -when the S series was pulled was at the same time that everyone was going for SUV's. These little cars were designed well for an everyday car from the smallish space they take up, the amount of interior and trunk room, and the lack of door dents. I think they could make one, built a little better, that would sell well again here in a few years but who knows about all the high and mightl new safety regulations and what they entail.

I still won't change my opinion on the sticks with a 10-15mph average speed commute though! I'm sure they could do a much better automatic now days but the car would also cost much more than the 11 year run.

Saturn Math

Reply #2 – June 19, 2009, 09:41:13 PM

I agree, a 5-speed in city traffic is the suck. When I had my '94 SC2 I lived in the city and had to do that stop & go bullshiznit. I had about a two-mile hill to drive up at an average speed of 1 MPH, too. It was OK coming down at 5:00PM, I could just leave the car in neutral and let gravity take over, but going up at 8:00AM was a pig.

Now, though, I live in the boonies. It's a 60MPH four mile highway drive just to go to the store. I go into the city twice a week, but I decide what time I go in, so naturally I avoid rush hour...

Saturn Math

Reply #3 – June 19, 2009, 11:11:46 PM

Perhaps the Saturn I had was slightly worn but the transmission wasn't quite as smooth as the late 90's Accord I drove recently (only manual I've driven since selling the Saturn late last year). This could have had something to do with my irritation too but either way a manual is a pain in gridlock and not much better in stop and go commuting. Besides the blue trail behind the car, it WAS enjoyable to drive down more "windy" roads if the A/C wasn't on. 124hp/122tq isn't a lot to play with but the motors do take a turbo pretty easily, as most overhead cam I4 motors can.

If I could find a decently priced low mileage '00 coupe, I would probably be tempted to pick it up (up to date interior with the old chassis but without the horrendous 01/02 body). I have to figure out why its insurance, liability only, was so expensive though! The insurance guy couldn't explain why. Any ideas?!

So why do people like the <97's more? Better heads or something? You would know as you've been around these things forever.

Saturn Math

Reply #4 – June 20, 2009, 08:11:09 AM

TC if you want a more accurate mpg result, fill the gas tank, then reset the tripmeter. Drive it down low on gas and fill it back up. Take the miles and divide by the gallons. That should give you an accurate number assuming correct size tires and accurate speedo/odometer. Try to use the same pump each time and pump the gas the same way too. I usually pump the gas til it shuts off and then go for one more shutoff. I dont like filling up to the filler hole.

Saturn Math

Reply #5 – June 20, 2009, 03:30:05 PM

Quote from: Thunder Chicken;278730

It sounds even better when I say it in terms of imperial miles per gallon, because imperial gallons are about 20% bigger than US gallons. An imperial gallon is 4.5 liters.

I used to buy Canadian whiskey in 40oz (imperial quart) size bottles.

Saturn Math

Reply #6 – June 20, 2009, 05:33:51 PM

i take it the saturn you have is the sl1(sohc model)?
i always liked those first and second gen saturns, somewhat roomy with decent gas mileage, but cracking motors :P

the delivery guy i worked with had a 93 4door sl1 with an automatic and he said he was getting 29mpg(combined, mostly crowded city) with no special driving technique.

Saturn Math

Reply #7 – June 20, 2009, 07:51:53 PM

Quote from: bhazard;278831

TC if you want a more accurate mpg result, fill the gas tank, then reset the tripmeter. Drive it down low on gas and fill it back up. Take the miles and divide by the gallons. That should give you an accurate number assuming correct size tires and accurate speedo/odometer. Try to use the same pump each time and pump the gas the same way too. I usually pump the gas til it shuts off and then go for one more shutoff. I dont like filling up to the filler hole.

That's pretty much what I did, except A) I only ran one tank through it so far and B) all of my measurements were metric, so I had to convert to get MPG. Gas is sold in liters and the odometer is in KM here.

Quote from: Ductape91;278919

i take it the saturn you have is the sl1(sohc model)?
i always liked those first and second gen saturns, somewhat roomy with decent gas mileage, but cracking motors

the delivery guy i worked with had a 93 4door sl1 with an automatic and he said he was getting 29mpg(combined, mostly crowded city) with no special driving technique.

This is the SL2 (DOHC) model. I was a Saturn mechanic for six years, so I know my way around 'em. I've seen eleventy-billion cracked SOHC heads, but never a DOHC one. The only major (IE expensive, IE "throw the car away") issues I've seen with DOHC models were oil burning (they all do), automatic transmission valve bodies going bad and causing problems (one of the contributing factors to my buying a 5-speed), and valves burning (and that, while not rare, was not really common either).

Of course there are some self-inflicted wounds that are fairly common as well, such as spinning the tires until the differential pin gets chucked out the side of the tranny, and seizing up engines (see "oil burning" above - lots of people run 'em dry), but needless to say since I'm aware of just about every Saturn issue I can certainly handle anything this car throws at me :hick:

Saturn Math

Reply #8 – June 21, 2009, 09:34:32 AM

I was just under the impression that since you said you put $35 in it, you hadnt actually filled the tank. I guess I was mistaken.

Saturn Math

Reply #9 – June 21, 2009, 11:49:17 AM

I didn't actually fill it, I just went by the number of liters I bought. I'm still buying gas and keeping track of the liters and the odometer, so a more accurate figure will be coming in a few weeks

Saturn Math

Reply #10 – June 21, 2009, 03:18:43 PM

Its actually pretty impossible to be accurate with that method. Trust me, I learned a lot of nerdy economy things after my bird blew up and I bought a festiva, cause that was really about all it was good at, besides hauling stuff. The only real accurate part of a gas gauge is when its pegged at full.

Saturn Math

Reply #11 – June 21, 2009, 05:11:39 PM

Ok, you've piqued my curiosity: How, exactly, would have buying an extra gallon of gas made it any less accurate than what I did? The math doesn't know whether the fuel pump "clicker" goes off or not.

...And I dunno what cars you're driving, but I have never, ever, seen a car with a gas gauge that was anywhere close to accurate at full. Every vehicle I've ever owned had a great deal of error at full. If I fill my T-Bird I can drive 100 miles before the needle even starts to move. The Sport I had (with star wars dash) would go 100 miles before the digital reading would stop showing "F" and start showing numbers. I have done it many times, filling up in Sackville, NS and making it to Liverpool, NS (on my way to Yarmouth, NS, where I've got family) before the gauge started to move, so I'm not exaggerating when I say 100 miles, either. And it's not just those two T-Birds. Every vehicle I've had, from the Lincoln Town Car to the Volvo V70XC to the three Saturns and every Nissan, Cherokee and F-150 in between has had roughly the same margin of driving before the gauge would start to move.

I WISH the gauge was most accurate at full, it would mean I could drive 100 miles without burning a drop

No, my friend, the "F" mark on a gauge is probably the least accurate part of it. Case in point: That $35 worth of gas I bought brought the needle to "F", and I'll guarantee I could've gotten another $15 worth into it before the pump clicked off.

The way I'm doing it, monitoring how much fuel I buy and how many miles I travel, is the most accurate way of determining fuel mileage without removing and draining the tank, filling it from a calibrated container, driving several hundred miles, then removing and draining the tank back into that same calibrated container and measuring how much fuel I've used. The more fuel I buy and the more miles I travel the more accurate my measurement will be, because the margin of error caused by gauge innacuracy will be reduced with every fuel purchase.

Saturn Math

Reply #12 – June 22, 2009, 10:12:00 AM

Its because youre going by the tank being full, not the gauge reading full. Forget about the gas gauge, youre right, it will never be accurate. The only real way to tell the tank is full is to actually make sure its filled up. So if you FILL it up, drive it down, and then fill it to the same level again, you can tell exactly how much you used. You cant fill it to a certain level on the gauge and then try to fill it to the same level again, because how do you even know how much you used, and how much to pump to get it to the same level?

Basically you should only use the gas gauge to tell you when to go fill up. Make your car happy and fill that tank.

Saturn Math

Reply #13 – June 22, 2009, 11:28:49 AM

The tank is designed to click the pump off whena certain volume is reached for venting reasons. Fill to click. Drive. Fill to click again to see how much you've used. Divide miles driven by this amount.

FWIW -- You'll never get a 100% accurate account due to expansion. You'd have to make certain that you were filling at the same pump at a time where the temp and barometric pressure were the same.

There's a reason why aircraft fuel/gas measurements are indicated in weight rather than volume.

Saturn Math

Reply #14 – June 22, 2009, 03:25:09 PM

I'm not using the gauge at all, bhazard, except to tell me when I need more fuel. I'm going by the amount of gas I'm buying, not by how high the gauge goes. Like I said in my first post, the first tankful, or even the second or third (I'm actually on the third now), will not be accurate, but at around the 7th or 8th it will be because the small margin of error introduced by the gauge reading at empty will be divided among several readings.

If, for example, the gauge has a margin of error of +/- one gallon when the needle is on E, and I go thrugh 8 tankfuls (~80 gallons) and travel 2800 miles (and this won't take long, I've already gone through ~50 liters (~13 gallons) and have driven over 750 km (~470 miles), and I've only had the car five days), that one gallon error is not going to amount to much. And it's still pointing to 36 MPG right now as I do the math.

You are right, though, that filling to "click", driving until empty, then filling to "click" again is a quick way of doing it, now that you've explained what you meant better, but I'd wager the margin of error between "clicks" on different pumps (the places I drive it would be impossible to be near the same pump when it was filled and again when it was empty - I'd almost certainly be 100 miles away when the needle hit E), or even the same pump at different times of the day, would be as high as my "several tanks" method.

It would also only provide a snapshot. If, for example, I filled the car and drove to Yarmouth and back, it would give me my highway mileage but would not give me an accurate measure of how much fuel I use during normal use. By spreading the average out over many tankfuls I'm getting a more accurate figure of how much fuel I burn when driving the car normally. It would almost certainly result in a higher than normal reading because I'd also be "driving for mileage". It would be too hard to resist, to try to get the highest figure possible. Going for the long shot ensures that my ADD will get the better of me and I'll lose concentration and start driving normally :hick:

There's also the "price of fuel" factor. Fuel prices are government regulated here, and we get advance notice when it's going up or down. The price is set every Friday. If it's going up, I buy lots of gas on Thursday. This happened last week, when it went up 15 cents/gallon ($35 worth being "lots of gas" in a Saturn, especially as I had to fill my considerably thirstier T-Bird, too). This week, however, all signs are pointing toward gas prices going down, so naturally I will buy it by the thimbleful until Friday, when it's cheaper.

Yeah, I know, that makes me a cheap-ass, but saving money on fuel was the whole point to buying a Saturn to begin with...

The other reason I have for not doing it your way is this: The main point of my monitoring the odometer was oil consumption. Fuel economy is just a side issue. I know the thing's gonna get mid 30's, because that's what Saturns do (and about the only thing they do well). My main concern was that I was going to have to re-ring this thing, since Saturns are well known for oil burning (and indeed, it was a quart low when I bought it). Thankfully, at 750 KM, the oil has not gone down a drop! My last Saturn would've already burned four quarts by now, before I re-ringed it...