Car Myth or Fact: Should You Top Off Your Gas Tank?

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Subject: So far so good

Driving a Lexus RX350 (new in 2008) now at about 138K and before that a Jeep Grand Cherokee which I bought new and got up to about 150K miles. Topped off virtually every fill. No harm experienced. And when I say topped off, I don't mean to the next dollar or a few more squirts of the nozzle. I mean to within 2" of the top of the filler neck. The nozzles vary in shutoff but generally get stopped (from splash back) with about 1.5 gallons of empty space left. I fill so high because I like to calculate MPG and that removes a significant variable. My most frequent filling location is about 3 miles from home so while that is not much it does mean enough gas is used on the way home to create a bit of a vapor space. And of course if I fill before driving someplace else, a larger space will be created quickly.

I would think if there were harm I would have noticed it by now. What if you were on some expedition and refilled from 5 gallon jerry cans? No warning about filling to the top with those.

I sure would not worry about rounding to the next dollar. As usual, YMMV.


Subject: Accidentally overfilled my car

I got a new car and accidentally overfilled it cause the pump didn't shut off. It spilled out. Is this going damage my engine? The article here said it may cause damage to the engine and cause it to run poorly. Does this article mean repeated habit of over topping or is one incident going to be fine. I never over top my car and it upsets me that the pump didn't shut off. I'm worried it could damage the engine and make it run poorly. Thanks


Subject: over filling gas tank myth

I've been driving since 1974. If you are a math wiz that's 42 years. I've been topping off my gas tanks both diesels and gasoline to the point that I have had fuel run out onto the ground hundreds of times and I have NEVER damaged any component on any of my vehicles. I am an engineer and have actually turned down an offer of employment from one of the big three. I will continue to round up to the next dollar for the rest of my driving days.


Subject: Perfect example of what not to do.

So you are the inconsiderate guy who makes my boots stink of gas for half the day!

Trust me, if everyone was as careless as you, and you had to live in a hot crowded city, you would find the air to be unbearable. You would find emergency rooms filled with asthmatics and those suffering with a dozen other respiratory aliments.
Many would die because of it - and do!
Air quality is not hippy mumbo-jumbo, it's a a quality of life issue, and a basic human right. Google 'China Smog' and see how these brand new gleaming metropolises are made almost unlivable thanks to their lax air-quality regulations and filthy air.

Besides, I and millions of other people can round to the nearest dollar without overfilling the tank. You are just a guy who simply doesn't care. - Apathy is an sociological disease which undermines even your community, sir.


Subject: Over fill with gas

I was told it it was bad for you to top up the car with gas. So I wanted to search further for answers and I got them!, then I started feeling sorry for my car....hahaha

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Hi, i worked in the automoble field for 8 years, I was the CIO of a large 8 location dealer group.


 Frankly, i would be leary of doing business with a company that is still pushing paint protectant or undercoating.  Undercoating is BIG no no as it will actually cause rust.  It traps water between the steel and the undercoating causing corrosion, it plugs up the door and rocker panel drains as well as drain holes in the uni-body frame rails.  The dealers cost for the undercoating is about 250.00 including man hours, it is a huge profit booster and nothing more.  Although Paint Protectant will cause no damage, it does no good.  It is nothing more than an acrylic polymer protectant which can be purchased at an automotive store...cost for the dealer including man hours, 75-100 dollars.  It is nothing more than a profit booster.


 Gap insurance is worth it, if you are involved in a collision and your car is a total loss, the insurance company generally pays you the trade value for the car.  Gap insurance will pay the difference between what the insurance pays you and how much you owe on the car.  for instance, if the insurance company pays you 2k dollars and you owe 3k, the gap insurance will pay the difference of 1k.  However, if you are finanacing 75 percent of the vehicle cost, then gap is not needed.


  Here is my best advice, pay for the car and not a single additional item.  Pay no more than 10 percent over cost, ask to see the dealer invoice, add 10 percent and pay that price.  Gap insurance can be purchased through the finance company after the purchase.


 So, if the invoice states the car cost the dealer 20k, you offer 22k and not a dime more as that is a fair profit for the dealer.  Puschase no other add ons, none.  If they wont show you the invoice, there are plenty of honest dealers that will.  I would be very careful with this dealer.


 Dealers also make money on financing.  for instance, they submit your loan for approval, the bank comes back and approves the loan at 6 percent interest.  The dealer will add 2 or 3 points charging 8-9 percent interest and the dealer gets the money for the points at the time of sale. Ask them how may points they are adding to the bank rate.


 I summary, be careful.  dont fall in love as there are many dealers with the same car.  Offer 10 percent over the dealer invoice and purchase nothing else.  if the dealer gets defensive, fails to show you the invoice, or pulls other sneaky tactics...WALK.  go to another dealer.


 I strongly recommend visiting visit to find the dealer cost for your car as well as many other informative car buying tips.




If it is the original timing belt, then yes - check your owners manual for the recommended changing frequency, but from a quick web search (not knowing your exact engine model) it looks like 60,000 recommended internal, and typically last 80-100,000 miles to failure if not changed.

The most frequent comment (and a red note items on manufacturer's website) is that you probably have a "zero-clearance" engine, an idiotic design that means if the valves are not fully closed when the piston come to the top, it hits the valves and breaks or bends them or punches a hole in the top of the piston. Talk about planned obsolescence !

In short, if that is the case and your belt breaks or gets so loose it strips the "teth" off it or slips, your valve timing will be off, and could cause catastrophic engine damage that would require a complete engine overhaul or replacement !

Unfortunately, after looking at a video on how to change the belt, they build it so almost all the auxiliary equipment has to be taken off to change the belt - the alternator, water pump, radiator upper hose, power steering pump, air conditioner, etc - so rough cost is $800-1200 ! If you are getting it changed, it is also recommended to replace the water pump while it is off.

Hopefully some Montero mechanic will hop on this question and expand on this, but NO engine belt of any type should be trusted to go 115K miles.

A great deal depends on the use of the vehicle.  If you do a lot of mountain driving or heave towing, then a flush would be necessary.  Under normal driving conditions, a flush is NOT necessary at 46K miles.  The shops make money on flushes, that's why they recommend them.  Most transmissions are good for 100,000 miles before requiring maintenance.  Your owners manual should say.....if not then leave it alone.  Maintenance is debated between a flush and a fluid drain and fill.  Both have merits and down sides.  Alternative Car Care is not a fan of flushes and will not do them.  We would rather drain the fluid and change the filter.

Assuming automatic transmission:

At a quick lube type place, with unknown brand of fluid - from about $30-60 depending if done as part of a general fluid change package or all by itself. If transmission fluid filters need replacing too (usually are changed with fluid change on an automatic transmission), more like $75-125 range.

At dealer, using OEM parts and fluid, about twice to triple that. Normal auto repair shop about halfway in between those two. One reason for higher price is they will not (if reputable) extract the old fluid through the dipstick tube and put in new - they will remove the pan or maintenance panel (which commonly has to be done fgor filter replacements) and clean the pan at a minimum regardless.

This assumes you do not need band or continuously variable shift friction surface replacement or adjustment, which can crank it up from $50-100 for band adjustment to several hundreds more for replacements.

Do NOT let some shop convince you to pay for a transmission flush - not only is it unnecessary, but usually uses contaminated fluid from other cars or harmful chemicals (sometimes even tap water or diesel fluid) and can seriously damage your transmission. If your transmission filters were not doing their job or you smoked your transmission fluid, the proper cure (assuming not bad enough to require transmission overhaul) is to change to new fluid and filters, then replace them again in a short time - typcially 50-250 miles recommended by manufacturers, to let the new fluid pick up the dirt and sludge and transport to the filters for cleaning.

IF manual transmission - from about $40-75 for one with drain pan and no filters, to as much as $200 range for one with filters that requires removing side panel to change filter and clean it out. Again, higher end at dealers.

My recommendation - ALWAYS require OEM fluids be used for all but engine oil - mixing brands and additives in equipment is just not a good idea, as they can react with each other and cause serious degradation of the lubricating properties, and even cause gel or sludge in the fluid. A transmission, transfer case, differential, etc should be able to run at least several hundred thousand miles without maintenance if you change the fluid as recommended and use only the same OEM fluids in it. The small amount you will save using cheap fluids is not worth the mega bucks to repair or replace a damaged unit. If you go to an auto shop, find out your required refill quantities and buy the fluids at the dealer and tell them to refill with those - just be sure to get enough to allow for a bit of spillage.