Failed Fuel Mileage Checks

[toobroketoretire]

I have made numerous attempts to check my fuel mileage on long trips and every one of them was screwed up because of some goofy problem:

1. On a trip to the coast and back my transmission's t/c clutch kept rapidly disengaging and reengaging which made a horrendous vibration and caused me to drive most of the way in 3rd gear.

2. On a trip to the coast and back I found my trip meter was adding an additional 5 miles for every 10 miles driven. As I didn't write my odometer reading down at the start I had no idea how far I had actually driven.

3. On a trip to the coast and back I found my vacuum advance had failed so my fuel mileage was much less than usual.

4. On a trip to Los Angeles and back I had 4 spark plugs foul (on the way back) which really screwed up my fuel mileage.

5. On my last trip to the coast and back my #2 cylinder quit firing so once again my mileage check was screwed up.

On Tuesday the 16th I'll be going to Santa Barbara and back (about 500 miles) and hopefully nothing will go wrong this time. I am hoping to get 16 mpg which would double the 8 mpg it started off with when it had the marine cam and TH400 with 3.08 gears. As usual I'll be making the trip with my 24/20 psi tires and .035" plug gaps to get the maximum mileage possible but this will be the first trip with my Ram Air and leaner #70 primary jets.

 

[LLC5]

I just gotta smile and shake my head.

Good luck on your trip.

 

[dougelam]

I'll take 11MPG for $20

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[Antz81]

In my small block '82 I run 20 psi front/17 psi rear and have done so for 25 years. And in my big block '71 I run 24 psi front/17 psi rear and have done so since I bought it in 2009.

As usual I'll be making the trip with my 24/20 psi tires and .035" plug gaps to get the maximum mileage possible but this will be the first trip with my Ram Air and leaner #70 primary jets.

Tire pressure is improving your getting closer to the recommended pressure though.

 

[LLC5]

Tire pressure is improving your getting closer to the recommended pressure though.

Baby steps dude.

I just hope he makes it there and back.....

 

[toobroketoretire]

Checking Fuel Mileage

Based on my past experiences something is bound to screw up again. This time I'll write down my odometer reading so I'll have two sources of miles driven and I'll bring my little solar-powered calculator along because I have forgotten how to do math as I got older (how many of you use a calculator for everything?). I just checked the charge of my A/C yesterday and it's still good and my windshield washer reservoir is full so other than washing my '71 beforehand it looks like it's ready to go. I'll be heading out around 3:00 A.M. so I can arrive in Santa Barbara around 8:00 A.M. and then I'll have my A/C on for the 250 mile return trip home. With luck my '71 will run the distance with no problems.

When I go on these longer trips I always drive a bit slower than the faster traffic and usually in the center lane so in the event of trouble ahead I can swerve to the left or right. And as I enjoy the view as I'm traveling I don't worry about passing slower traffic ahead of me until I have the opportunity to do it safely. I always get amused over impatient drivers who DANGEROUSLY pass everyone and then 25 miles down the road I find they're just 100 yards ahead of me. I have a cheap $50 Harbor Freight radar detector that does a good job and I only use it to remind me of my speed; not so I CAN speed.

I am hoping to get 16 mpg and with my Ram Air and leaner #70 primary jets I may accomplish it.

 

[toobroketoretire]

Tire Pressures Required In C3's

Every tire has it's MAXIMUM LOAD and MAXIMUM PRESSURE on the sidewall and when you run half the maximum load you only need half the maximum pressure. It's as simple as that. But rather than running half the maximum pressure I run a couple of extra psi for safety reasons and that's why I have always run 20/20 psi in my '82 and 24/20 psi in my '68 and '71 with their heavier big block engines. And...................I get over 50,000 miles out of my tires or about twice as much as you get running 30-32 psi. You must inflate your tires according to how the tread wears and when you see the middle is worn out when the sides still have 3/8" of tread it means they are grossly over inflated.

 

[Earthway69]

Thx for the tip. Always run 28/28 psi and rears wear in the center. Will try 22/22-24/24.

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[SVO]

Thx for the tip. Always run 28/28 psi and rears wear in the center. Will try 22/22-24/24.

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Earthway, you are falling into a troll trap. If you choose to follow any advice offered up by TooBroke, you need to exercise extreme caution in doing so.

 

[dougelam]

This is what I found so far,

I would think that the lower the air pressure the less stable the tire becomes!

But then again I myself run 27PSI on all 4 corners on my C5 w/stock tire sizes

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[82ColEd]

Why wouldnt you follow whats posted on the sticker in your car?

Over or under inflating your tires can either wear them early or ruin your fuel mileage or be actually dangerous..:confused ;squint:

 

[toobroketoretire]

Tomorrow (August 16th) is the big day but based on my past experiences something is bound to screw up. Right now it's running perfect but a lot could change in the next 24 hours. As the trip involves driving over the Tehachapi mountains with their 5000 foot elevation the mountains will take a toll on my fuel mileage but I'm still hoping for 16 mpg.

 

[Vettehead Mikey]

Thx for the tip. Always run 28/28 psi and rears wear in the center. Will try 22/22-24/24.

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I believe that falls way out of the range recommended by GM. Beware following advice from 'some guy on the internet who said....'

 

[toobroketoretire]

Speaking of fuel mileage checks I checked the volume of my '71's tank right after I bought it and it held exactly 17 gallons with it filled to the middle of the 3" neck. And when it's filled the indicator needle JUST reaches FULL and when the needle reaches EMPTY it has 5 gallons left. Nice to know when I'm running low on gasoline as I can estimate how much further it'll go before it quits.

On the trip to Los Angeles in which 4 of my spark plugs quit firing I pulled into a gas station and it died right when it reached the pumps. It swallowed 16.95 gallons. Talk about cutting it close!

 

[82ColEd]

I believe that falls way out of the range recommended by GM. Beware following advice from 'some guy on the internet who said....'

From this link: GM

WHY IS TIRE PRESSURE IMPORTANT?

Air is a gas, expanding when heated and contracting when cooled. For most of North America, fall and early winter are especially important times for checking tire pressure on your Chevrolet vehicle — as the ambient temperature falls, tire pressure goes down. A good rule of thumb: with every 10 degrees Fahrenheit of temperature change, tire pressure changes about 1 psi – higher as temperatures rise, lower as they fall.



What happens if your Chevrolet tire is underinflated?

• Premature or irregular wear
• Poor handling
• Reduced fuel economy
• Overheating, which could lead to a blowout

What happens if your Chevrolet tire is overinflated?

• Unusual wear
• Poor handling
• Rough ride
• Greater risk of damage from road hazards

Look for this sticker in your door jamb, it has filled in info for YOUR car and thats what i go with.. Obviously you can do whatever you like, but... :ugh

Stefan

 

[toobroketoretire]

Disappointed

I am very disappointed after yesterday's Santa Barbara trip. I never got the 16 mpg that I was hoping for but rather an average of 13.576 mpg. So it looks like the higher sustained speeds of freeway driving actually reduces the mileage. My '71 ran very well but the speedometer was reading almost 20 mph slow on the way down but read correctly on the way back and my driver's window spring broke when I powered the window down. I had my A/C on the entire return trip and I was running 75 mph most of the time so that reduced my fuel mileage even further. As usual I got several compliments on my '71 as most folks love these chrome-bumper C3's.

 

[toobroketoretire]

On my way home and as I was driving over the Tehachapi mountains I noticed it was awfully hot outside. My coolant temperature reached about 215+ degrees at about 70 mph which is the hottest I have ever seen it when I was running at higher speeds. But as this is August the higher temperatures are to be expected. I got 4 more compliments on my '71 yesterday as everyone seems to love the chrome bumper C3's.

 

[toobroketoretire]

On my way back from Santa Barbara I found myself running 80 mph a few times but didn't know it because everyone around me was running 80 mph. But I also noticed I was barely touching the gas pedal and just an itty bitty push on the pedal sent it past 90 mph in the blink of an eye. Boy, these 454's sure have a lot of torque and when combined with a TH700R4 and low 3.70's they're just plain awesome.

This morning I discovered my air restriction indicator's piston had moved about 1/4" because my filter was a bit plugged. The indicator is so sensitive ANY full throttle will move the piston even with a new filter installed. But after getting used to it I can tell how much my filter is plugged by observing how far the piston has moved. About 99.9% of my driving is at 2500 rpm or less so when I see the piston has moved I know it's time to clean the filter by simply blowing it from the inside out using 125 psi of compressed air.