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Gas Mileage


Bstock

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Hey guys,

 

I bought my datsun with the primary goal in achieving decent gas mileage and I was expecting anywhere from 30-40. Granted yes the car is old but Im curious to know how other vehicles are doing on MPG. I am currently getting around 23-25 within the first two weeks of driving. I read a specific article bragging about how the B210 sips on gas, but I got say right now its looking like my car is fresh out of the desert and thirsty! I plan on changing all my fluids this weekend to see if that makes a difference.

 

Thanks

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What year is it and what engine and transmission does it have? I have an 81 210 wagon A15 5 speed. When it was bone stock I got the highest of 38 mpg driving 45-55 mph at high altitude (Yellowstone national park). My highway average was usually 27-35 mpg though depending on lots of variables like gas station, winds, average speed, tire pressure, etc. I finally ditched the stock setup now and put on a ported/built head, GX cam, Weber 32/36 dgv, lightweight lifters, 2.5" exhaust, and new 15" wheels/tires. I gained decent power but gas mileage is only at 29 or so at 77mph on the freeway. The carb is tuned as good as I could get it, cruise A/F fluctuates around 13.5 to 14.5 so there's more to be had but not a ton. This carb is kind of a butt head for steady A/Fs. EFI would definitely help a ton but is going to cost a bit to get setup.

 

The super high mpg's these got was when they were newer, in better tune, we had better gas without ethanol, and the speed limits were much lower at the time. If you can get it tuned really well and stay easy on the gas pedal using non ethanol gas, get everything on the car in tip top shape, and drive it frequently on long distance trips to keep the internals clean you 'might'see those high numbers again.

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How you drive it affects the mileage most. Flooring it from stops and revving to red line on every shift around town. Exaggerated, but that sort of thing.

 

City driving will give the worst mileage from all the stops and starts. Just imagine that every time you have to slow down you are throwing away all the gas used to get up to that speed. Look up ahead and anticipate stops that are coming and begin to slow well before then. In town if there are two lanes I keep to the left so that you avoid drivers who slow to turn right or drivers entering your lane that force you to slow. Leave more room between you and the guy ahead. This avoids you  getting on and off the gas constantly or worse... hitting the brake. Drive like there is an egg under the gas pedal.

 

GO THE SPEED LIMIT.... weird but you actually get better mileage doing this. On the highway it's mostly air resistance the car has to push through. So keep in mind that to drive at 60 it takes 4 times as much energy as driving at half that speed, not half as much. Take the slow lane and drive the limit, faster traffic can simply go around you if they are in a hurry.

 

All this take much practice

 

 

The car may also be at fault. Choke not shutting off fully. Valve lash not set properly. Ignition timing not set properly. Points worn out. Thermostat stuck open not letting the engine up to proper running temp. Even a brake dragging. Tire pressure too low. Carrying excess 'junk in the trunk'.... every extra unnecessary pound takes gas to bring up to speed.

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You have to tune up old cars.  That means everything Mike suggested.  I would also do a compression test.  One of the best ways to more power, and more economy is good rings, a good valve job.  Things that improve the power of the engine by adding efficiency will also improve the economy when you are not demanding the power.

 

I would avoid getting into a trap of spending a lot of time, and money on trying to get minor improvements in gas mileage, other than a good tune up, tire air pressure, or putting the engine into good shape.  Lets say the simple things suggested get you up to 35 MPG, with careful driving.  If you spend another $500.00 on improving the gas mileage further,  well, that $500 can buy a lot of gas. even at $3.00 to $4.00 a gallon.

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One other thing is to check that the vacuum and mechanical advance are working.

 

Oversize tires will go farther than showing on the odometer. Just 1% will take you 25 miles farther on a 250 mile tank full. 10 gallons @ 25 MPG over 275 (real) miles will correct your MPG to 27.7 MPG from 25

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Ah cool thanks for the inputs guys. But as for the vehicle its a 78, 4 speed, 1.4L. and as for how I was driving it, I took it up to my brothers house in Canada so mostly highway miles but with it being a 4 speed just holding 60-65 was revving it pretty high. For the next two weeks I will only be commuting to and from work so I think that might give me a more realistic mileage.

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I'm guessing a good B-210 might go 100MPG on a good day. This would be about 5,800 on the 13 " tires and a 3.90 diff.

 

One of the hypermileage guys was getting I think 70 over the length of a course with one.

 

A big factor on the mileage for a B210 is the transmission, you will get the biggest gains going to a 5 speed from a 4 speed. Should be able to do 65 at about 3000rpm.

 

On the freeway with an A14, Hitachi carb, 5 speed transmission, Premium, and larger tires, I got mid-high 40s between Portland and Sacramento, and that was with a fully loaded car and going over the Siskiyous. 

 

Driving in town I got low to mid 30s, and 27-29 if hitting heavy traffic and lots of starts and stops.

 

Now, change the Hitachi out for a properly tuned Weber carb and that shifted down about 5mpg overall but seems more powerful.

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I want to make this kind of mileage a real thing for my car! I cant say I am overly concerned with power. I want my car to look good and get some good mileage, that will make me a happy owner. I guess one of the first things i could easily do is get some larger wheels and tires. Ill be sad to see the honeycomb caps go if I do go that route.

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You can buy taller 13" tires and not replace the rims. But then the speedometer reads incorrectly and you don't know your true mileage. It also lowers acceleration performance and makes it sluggish.

 

Start with a good tune up including setting the valve lash and timing. This is the cheapest way to get the most out of your gallon of gas.

 

The transmission and differential oils should be replaced every 30K so if you don't know when they were last replaces or even checked, better just change the now. GL4 90w for transmission and GL5 90w for the diff. Do NOT use GL5 in the transmission. Transmission oil bust be copper alloy safe to use. You can substitute a synthetic transmission oil which is thinner and lubes better but it may start to seep out the rear seal. I use GM Delco Synchromesh Transmission Fluid in my 5 speed and it much improved the up and down shifting and specially when cold. I replaced the rear $5 seal and no problems. The Delco oil is thin like 10W30 engine oil so there may also be some improvement in mileage too.

 

I avoid synthetic engine oils, they are toooooooo expensive for any gains in an old Datsun. That, and synthetic is so slippery it will leak out of old engine seals and gaskets.

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Well in a way he's right, GL5 has more extreme pressure anti scuff additives than GL4. But it's needed in a differential as the gears work much differently. I think because power is transmitted through a 90 degree turn and the gears rub differently than a transmission where the gears are aligned in the same front to back axis. More importantly.... the sulfur additives will bond with the surface molecules of the copper alloy synchromesh rings forming a hard surface protection against wear. However the copper beneath can't support this (think sheet of glass on a soft sponge) and it cracks and falls off. This is repeated over and over eroding them. The synchro rings can handle about 4% of this anti scuff protection. GL5 is about 6%. You might think "how can 2% make all that difference?" Well it isn't 2% it's really 50% more if you think of it. GL4 is good for transmissions or anything marked 'yellow metal' or 'copper compatible' on the bottle. If in doubt what you have don't use it.

 

 

Well used synchro ring from one of my B transmissions.

 

y5xxXQC.jpg

 

 

Notice the tarnish on this brass synchro ring? Takes time but ultimately GL5 is not good for your transmission. If you had to use it to 'get home' there's no problem, just replace it later with GL4

 

OXhRWFg.jpg... not me

 

Transmission oil should be replaced every 5 year / 30K miles.

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Awesome thanks for the tips. Ill need to return a bottle of the GL5 cause the guy at the store convinced me that it was a substitute to supercede GL4. Ill take a look at that seal to see how it is holding up.

Keep the GL5 for you rear differential. Works fine there. You'll want to change that too. 

 

Undo the top fill plug first, then drain from the bottom plug. 

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Made some progress today, Changed the Alt belt and the smog belt, did an oil change, replaced my air filter and fixed my temp gauge. Unfortunately I got rained out and called it a day before I made it to replacing the trans fluid.

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Just has an FYI; I once used the GL4 / GL5 combo stuff and after one track day I drained the fluid and it had this lovely good metallic sheen floating on top of the fluid. That was obviously synchro dust, NAPA has Sta-Lube GL4 it does the job well.

 

As for the mileage, once upon a time I had a 4 speed B210 and on the highway it got maybe 30mpg. I managed 27 mixed driving. If you keep the car to 60 or below you may manage 32. To get the most mileage you have to keep the motor below 4000 rpm.

 

As for RPM, A-series motors will rev their guts out all day long. On a coupe of road trips we've driven them at 5500-6000 rpm for up to an hour at a go. The motors in my race1200 never go below 5000 rpm, I use standard, rods & pistons and rev them to 8200. The only thing that needs to be changed is valve springs. The stock springs will float around 6800. These motors are non interference fit so you're not likely to damage anything. I've bent a valve once but that was because I was revving it to 9000 rpm in second gear in a futile attempt to get past an Alfa GTV. The damage was done not because the valves floated but the adjuster back out and the push rid wedged under the rocker. When the motor went off song instead of shutting it off I tried to limp it in.

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How is changing the fluids help with MPG?  Maybe tune up is better?  Do you have a book?

I figure if the fluid is old, things aren't moving as efficiently as they could be. But yes I will be doing a tune up this weekend as well now though, I do also have the maintenance book for the car.

 

Thankfully I did finally find that darn GL4 specific fluid, I was able to pick it up at some small mom and pop auto.

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Redline MT90 and many of their other options are GL4, and if you can find it locally its about the same price as the Sta-lube GL4. Also if theres a Harley dealer around and you can't find any GL4, Redline fluidfor Harleys is supposed to be GL4 and the right weight too.

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If you switch to a hotter coil and pull positive voltage directly off the battery, you can increase mileage by 2 or more mpg.  You get a hotter spark that way as the input voltage is 14 volts instead of 12.

 

Some will say this is bogus or may cause damage to the engine.  I did this with a 78 lemans and consistenly increase mpg from 15 to 17.5.  On my B210 I get about 3 mpg more.  And I have been running it this way since '08 with no issues.

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The high MPG 210GX used the NGK BP5EQ-II multi electrode spark plug, precursor to the E-3 but better

 

People over tightened the wing-nut on the air-filter lid and warped the top of the hitachi carb which caused flat spots on excell, you can pull the carb top and make it flat again with your Datsunhamer 

 

Stock hitachi coils put out 58kv most aftermarket only 38kv, careful selecting a replacement or you will go backwards

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