: Increasing My Gas Mileage...



CadiPunk
01-21-09, 03:58 PM
I've got a 1990 Brougham. All stock with the 5.0L 307 V8. My question is, what can I do to increase my gas mileage? I know the most obvious answer would be "buy a new car" but, I love this car and just wanted to know if there was anything I can do.

Thank you
Danny

jayoldschool
01-21-09, 07:41 PM
What's your actual full tank to empty mileage now? Highway, city, or mixed? We need to know where you are starting...

Brougham91
01-21-09, 07:48 PM
The biggest change you can make immediately is to drive at a moderate speed. Your engine is more fuel efficient at 50 mph than 60 and at 60 than 70.

I found that I have a much easier time driving the speed limit in my Brougham than I did when I had other cars; I love being in my Brougham, so I am in less of a hurry to get wherever I am going. :)

Other really easy tips are to make sure your tires are fully inflated and you air filter is clean.

If want to get nit-picky, you can try to catch as many green lights as possible, so you come to dead stops less often. This requires driving near the speed limit, easing off the gas a fair distance from a red light and paying attention to turn arrows and crosswalk indicators to figure out when the light will go green. This tactic isn't very helpful in heavy traffic but is pretty easy to do when few cars are on the road.

If you want more suggestions, google the word "hypermiling" and there are all sorts of ideas -- some good, some stupid -- out there about how to get the absolute most out of your gallon. Most of the hypermilers drive tiny, newer cars, but a lot of their ideas apply to vehicles of any size.

caddeville89
01-21-09, 10:41 PM
The biggest change you can make immediately is to drive at a moderate speed. Your engine is more fuel efficient at 50 mph than 60 and at 60 than 70.

Other really easy tips are to make sure your tires are fully inflated and you air filter is clean.

If want to get nit-picky, you can try to catch as many green lights as possible, so you come to dead stops less often. This requires driving near the speed limit, easing off the gas a fair distance from a red light and paying attention to turn arrows and crosswalk indicators to figure out when the light will go green. This tactic isn't very helpful in heavy traffic but is pretty easy to do when few cars are on the road.

If you want more suggestions, google the word "hypermiling" and there are all sorts of ideas -- some good, some stupid -- out there about how to get the absolute most out of your gallon. Most of the hypermilers drive tiny, newer cars, but a lot of their ideas apply to vehicles of any size.

:hide:Not to be my usual disagreeable self, but I think alot of what you said here has been disproved as myth. About the only one I would say is ultimately true is the one about keeping your tires inflated.

From my own personal experience, and having talked to many mechanics about the issue, I have to say I disagree that 50MPH is the "ideal" speed for my car. It seems for me to be more like 65-70MPH, even without having overdrive. This might not be true universally, though generally speaking, on newer model cars with smaller engines, this is true. There is also much controversy over whether slowly coasting through lights saves gas as well, especially with bigger model cars. Many believe they actually get better mileage with moderate acceleration at lights.

There are many variables. Many people now are calling for the re-instatement of the 55MPH speed limit, even though it was proven to be counter-productive to saving energy on the whole, even if it improved fuel economy on an individual basis. I understand from the minimal research I have done that Ethanol will sap your fuel economy and power, due to it's requiring more energy to burn (aside from damaging your engine and fuel system in other ways).

Considering the controvercies over what does and does not save fuel (or what is worth going through to save fuel), I find it amusing that some European countries are requiring the use of hypermiling techniques in order to get a license. Maybe the money used to install and enforce such legislation should be used to develop, for instance, solar panels that the average homeowner could afford to buy, reducing fuel used to produce electricity, or cars that get hundreds of miles to the gallon instead of tens (like the pogue carburetor did in the 1920's or 30's).

One thing I can say that should be obvious: keeping your car well maintained is probably the best way to maintain fueal economy. Missing or damaged trim panels or an engine that has never had the oil changed are non-starters for the fuel-miser. Incorrect timing, plugged EGR and lots of other issues will not help either.

Hope I've been enlightening!

dirt_cheap_fleetwood
01-22-09, 11:27 AM
Just drive good and easy. On the highway, just do the speed limit. On my Fleetwood I get about 2-3 mpg less driving at 75 than I do at 65. You have to remember that these cars were built back when the national speed limit was 55 so they are not designed to do much over 70. Also, try to hit the lights like Brougham 91 said. Remember, every time you hit the brake pedal you are wasting the energy (gas) that it took to get up to that speed. Theoretically if you never hit your brakes in stop and go driving (coast to a stop) you would get the same mileage as if you were on the highway because although it takes a lot of energy to get the car going none of it goes to waste from braking.

Also keep your car tuned up and working right. Make sure you have a good air filter and that your ignition system is working properly. Keep the oil changes up to date because dirty, gummy oil will have an effect on mileage as well.

jey
01-22-09, 01:20 PM
Yes it's the stop and go that really ruins gas mileage. I rented a Pontiac G5 and drove it only through rush-hour traffic and averaged 22 mpgmpg. It was getting 33 when I was just on the highway. Hypermiling is even more beneficial on a big car than a econobox - the difference between 17 and 13 mpg is huge - who cares about improving 30 mpg to 34.

Another tip is don't idle your car for a long time to get it "warmed up" - just drive gently. The engine is most wasteful when cold - better to get going and warm it up faster.

At high speeds the aerodynamics do start to count against your gas mileage significantly. I found I could still get 24 mpg when averaging 75mph, but 80+ it dips to 20 or worse.

dirt_cheap_fleetwood
01-22-09, 03:04 PM
Another tip is don't idle your car for a long time to get it "warmed up" - just drive gently. The engine is most wasteful when cold - better to get going and warm it up faster.

Oh, forgot about that one. An engine is horribly inefficient when it is cold. When you start it up just wait until the choke turns off and then you can drive it easy until the engine is fully warmed up. Also, if you have to make multiple trips, go to the furthest destination first. This will let the engine fully warm up and it will stay warm as you stop at each destination on your way home.

My_favorite_Brougham
01-22-09, 03:48 PM
Make sure you have good spark plugs. Soiled ones cause less combustion, less power, and more gas burned/wasted due to a rich mixture. I replaced some 10 year-old plugs in my grandmother's car and it gave it a significant power boost - so much that you don't need to floor it anymore to get somewhere.

Also make sure you have a good thermostat. I have 1983 Oldsmobile with the same engine as yours, and the thermostat is stuck open. Consequently the engine never warms up, and I'm getting several mpgs less than I did before.

sven914
01-22-09, 09:17 PM
Oh, forgot about that one. An engine is horribly inefficient when it is cold. When you start it up just wait until the choke turns off and then you can drive it easy until the engine is fully warmed up. Also, if you have to make multiple trips, go to the furthest destination first. This will let the engine fully warm up and it will stay warm as you stop at each destination on your way home.
They are right that a cold engine is inefficient, and you should not let it idle for extended periods, but driving around with a cold engine wastes more gas than letting the engine warm up. Also, over time, driving a cold engine will ruin it. With my 89 Brougham, with a .307, when I start it, the first thing I do is turn on the defoggers and then hit auto, to get cold air blowing out of the floor vent. As soon as warm air comes out, the engine is warm enough to be moved.

Some other things you can do are using Gumout, with Regane fuel system cleaner, changing all dirty filters (including fuel filter and transmission filter), check for correct vacuum line routing (make sure there are no air leaks), make sure the engine is mechanically sound (have it re-timed, repair any leaking gaskets) and keep to a regular maintenance schedule (including replacing plugs/wires, flushing and/or changing all engine, transmission, and differential fluids, and have the chassis properly lubed). Doing this allows me to go an average of 2 weeks between fillups, and obtain an annual fuel millage of 16mpg (highway/city), and I let her idle for 15 minutes every morning.

csbuckn
01-22-09, 11:54 PM
Its getting deep in here. Other things...replace OLD vacuum hoses, not just the ones that are obviously bad...cap, rotor, wires and plugs...keep your oil up to date...no drag in suspension(get an alignment)...and if you got the know how or money, rebuild the carb.

jey
01-23-09, 04:01 PM
Also weight is an enemy of fuel efficiency - if you have a lot of heavy useless stuff in your trunk clean it out.

sven914
01-26-09, 09:51 AM
I've also found that my car warms up faster after I removed the cold air intake. I don't know how cold it gets where you live, but I’d take it off anytime it’s below freezing, and going to be for a few days.

ShadowLvr400
01-26-09, 10:32 AM
Oh, another one, go on a diet with your car... You can decide how drastic you want to be, but every bit helps. So that box of tools in the trunk, can go, the 4 golf bags, can go, the bags of cat litter, can go. There's a rough formula like the 100 lbs equals .1 seconds in the 1/4 mile, but I can't remember the economy one. If you want to be really drastic and yank the spare tire, the back seats, the carpeting, etc you can, though that's a bit excessive IMO. But losing weight on the car is a good thing.

caddeville89
01-26-09, 06:05 PM
Yah, I can think of times where I was glad I didn't remove the spare tire. I mean, if you're really getting to the point that you're removing the seats and carpet of a FWB to save a few hundreths of a gallon of gas per mile, then you probably chose the wrong car to be driving in the first place.

CadiPunk
01-29-09, 12:36 AM
Thank you for all of your replies!

Most of that I have heard through the grapevine or from research I've done.

What I would like to know is: Are there things I can do to my RWD 90 Brougham that will improve my fuel economy?

Aron9000
01-29-09, 01:39 AM
I got 23.5mpg in my 1991 with the 350 on a road trip doing a steady 80mph. I usually average 18mpg doing a 60/40 mix of highway and city driving. Gear ratio is a 3.08 BTW. I consider it excellent mileage for a big old boat shaped like a brick.

Just for some reference numbers. I don't know if your 307 will get any better mileage since its carbed and not fuel injected.

sven914
01-31-09, 11:13 PM
Thank you for all of your replies!

Most of that I have heard through the grapevine or from research I've done.

What I would like to know is: Are there things I can do to my RWD 90 Brougham that will improve my fuel economy?
If you really want to get technical, adding a turbocharger or a supercharger increases the volumetric efficiency of an engine, and will marginally increase gas mileage.

Aron9000
02-02-09, 07:47 PM
If you really want to get technical, adding a turbocharger or a supercharger increases the volumetric efficiency of an engine, and will marginally increase gas mileage.

^ Forced induction might increase your fuel mileage on paper, but in the real world it doesn't. If you stay out of boost, your mileage is okay, but driven hard, forced induction cars get really shitty mileage. And if its turboed/supercharged, it probably has a lot of power and you're having fun flogging it:D

My LS1 powered Camaro got much better mileage than my friend's Evolution(20mpg vs 15mpg)

jey
02-03-09, 11:18 AM
If you stay out of boost then you're not experiencing the theoretical efficiency increase either.

In the real world there are challenges to getting real efficiency increases with forced induction, on top of a heavy right foot. Forced induction cars need higher rpms to stay in boost, so shorter gears are fitted. But these shorter gears kill highway fuel efficiency (the comparison of the 5-speed EVO vs. a torquey Camaro demonstrates this well.) Also, intake temperatures are high in FI setups, especially turbos. Therefore to avoid detonation stock turbo cars run pig rich, which is again awful for fuel economy.

Take a look at a proper German FI car if you want to see efficiency, not these riceboxes. Try the MINI Cooper Works - 208 hp and 26/34 mpg. Or the Audi TT.

sven914
02-03-09, 11:13 PM
Also when you super/turbo charge an engine you have to make sure that it can handle boost. If the stock compression ratio is too high to be compatible with the amount of boost the charger is capable of, then you'll end up with a bunch of pieces in your oil pan. Before running boost, you should also go through the internals of the engine and replace any worn or weak parts.

And running boost CAN increase gas mileage, but it has to be in smaller amounts. If you run boost to point where your engine is above 120% efficient, then your actually burning more fuel than necessary. A naturally aspirated engine runs around 85-90% efficient, so if you run boost to bring it to 100% then you will have reached your engine's optimal efficiency.

But, once it's all said and done, it would be cheaper to just make your car run as good as it did on the dealer's lot then it would be to turbo/super charge it. (And running boost sometimes requires an upgrade in your gasoline's octane rating to overcome detonation)