Ask A Car Nut

[dIZZyBlIZZy]

I feel like an auto noob asking this, but is there a significant boost in gas mileage for taking higher-octane gas? Significant enough, say, to outweigh the extra $.10 per gallon that it normally costs?

The reason for high octane gas at the pump is because some cars have much higher compression ratios. These cars (most notably the 4.9L Cadillac), when running standard unleaded gas, cause an incident in the cylinder called detonation, sometimes called knock or ping. This is caused by a cylinder firing, and a second ignition within it, colliding. It will cause serious damage to your motor including snapped rings and scorched heads. If your car calls for it, use it; but if you don't have to use premium, you should never need it.

This is a what detonation is.

 

[Formaldehyde]

I feel like an auto noob asking this, but is there a significant boost in gas mileage for taking higher-octane gas? Significant enough, say, to outweigh the extra $.10 per gallon that it normally costs?

No, not at all. You get no additional power from higher octane fuel unless you have a significantly higher compression ratio or turbo boost, which is common in race car engines. But higher octane fuel in a street car engine that has a low enough compression ratio to not require it will just make it run a bit cooler.

As dIZZyBlIZZy pointed out, there are some engines that do require higher octane fuel on the market, but they are fairly few and far between these days due to DMEs and knock sensors. The DME simply retards the spark when the engine starts knocking. This will hurt the power output to some extent, but it is an easy way to save some dinero and will protect the engine if you have to use lower octane gasoline in an emergency.

I've been told it works out more expensive, but that a full tank once or twice a year should clean out the injectors. Basically the same as sticking redex in the tank.

Higher octane fuels do indeed typically contain additives that will clean your fuel injectors. But there isn't that much per tankful so you really have to run it all the time to get that benefit.

Unless you run the specially formulated higher octane fuel on a regular basis, it makes far more sense to just add a bottle of fuel injector cleaner once every oil change or so. For instance, a 6-pack of Chevron Techron Fuel System Cleaner goes for $22.88 on Amazon.com and is available from any Chevron gas station as well. Red Line sells for $9.95 on Amazon. All their products are outstanding. Swepco 503 is also highly recommended, but it is a bit more difficult to find.

 

[rugbyLEAGUEfan]

1.Your choice of a free Ferrari or Lambourghini ? Any model you want .

I'd be happy with a Contash

2. Do you agree that "There is no substitute for cubic inches ?"

 

[Formaldehyde]

The new Lamborghini Aventador J Speedster is mighty tempting. That is, if I could steal it from the apparently sole owner...


Link to video.

But I think I'll still stick with the old-school Ferrari F40.


Link to video.

 

[Smellincoffee]

If a reasonably intelligent and curious but completely inexperienced person (such as myself) expressed an interest in learning basic automobile maintenance and repair, how might you advise them? Are there any books which are actually helpful, or would knowledge have to be learned first-hand, by watching a patient mechanic and using him as a teacher?

(My father has always been a good mechanic, but as a kid I disdained 'dirty work', so I never learned anything. It's only in recent years that I've developed an interest in self-reliance and appreciation for "real" work.)

 

[Formaldehyde]

It really isn't that difficult as long as you have basic mechanical aptitude, e.g. you can turn a screw without stripping the threads, and you know that you can't over-torque smaller fasteners or they will break.

Edmunds has books for just about any make of car that will give detailed instructions about how to replace just about any component. Many car vendors now even have free factory repair manuals online.

Of course, you have to be able to diagnose what has failed in the first place. That does take a certain amount of experience and the ability to think analytically unless it is obvious.

At a minimum, you need a set of open/closed end wrenches and a set of 3/8ths inch sockets along with a socket wrench and extenders, a set of 1/4" nut drivers, as well as regular and Phillips screwdrivers. If you are going to work on modern cars, you will also need a set of torx screwdrivers or torx extensions for your nut driver.

All of these can be purchased at Sears at nominal cost. I would recommend getting the Craftsman tools because they are high quality and have a lifetime replacement guarantee. You can buy similar tools elsewhere, but you have to be careful to only get high-quality ones. Bad tools will result in stripped fasteners and lots of hassles that will quickly cost far more than the cost of decent tools. You should be able to pick up the basic stuff for less than $100.

Here's a starter set for $50:

http://www.sears.com/shc/s/p_10153_...4&i_cntr=1331510589580&sid=IDx20070921x00003a

And here's an even better set for $120:

http://www.sears.com/shc/s/p_10153_...921x00003a&ci_src=14110944&ci_sku=00927006000

The best thing to do is to start out with basic maintenance chores, like changing the oil, changing the air filter, replacing brake pads, and the like. As you gain more familiarity, you will soon be able to tackle more difficult tasks.

Much of what you need to do will be underneath the car, so you will also need a decent jack and a set of jack stands before too long.

You probably know one or two people who work on their own cars. They can be a great help to get started. And they can help out when you inevitably get stuck. Most of the time it just takes a bit more "persuasion" than you think is necessary. A jar of hand cleaner like Go-Jo and a pair of mechanics gloves also come in handy.

 

[dIZZyBlIZZy]

As dIZZyBlIZZy pointed out, there are some engines that do require higher octane fuel on the market, but they are fairly few and far between these days due to DMEs and knock sensors. The DME simply retards the spark when the engine starts knocking. This will hurt the power output to some extent, but it is an easy way to save some dinero and will protect the engine if you have to use lower octane gasoline in an emergency.

Do the 4.9L Caddies have the DME?

Also, do you specialize in a particular model or era (ie prewar, tri-5, contemporary exotic)?

 

[Formaldehyde]

All modern fuel injection cars have DMEs, but for some odd reason the 4.9L Caddy engine didn't have a knock sensor.

I have a passing interest in any motorized vehicle, but I have paid a lot of attention to sports cars and autocrossing / road racing in particular.

Speaking of which, I just watched the SEMA Ultimate Street Car invitational on Speed TV and I know 4 of the competitors featured on TV from my autocrossing days. The overall winner was 5-time SCCA Solo II National champ and 2-time Pro Solo National Champ Danny Popp. He would have lost because his brake master cylinder failed before he could finish competition, but one of his competitors loaned him the part off his own car so he could complete the last event.

Here is Danny working his way to the front in a 2008 NASA qualifying race at Mid-Ohio/ He started from dead last and finished 2nd overall and first in class:


Link to video.

Here is one of the top finishers, 11-time SCCA Solo II National champ Mary Rice Pozzi, making a fun run in a friend's car:


Link to video.

Here she is hyping the sport, as usual:


Link to video.

 

[classical_hero]

Link to video.

How cool would it be to do that? Also what do you think will be the next innovation in cars?

 

[Formaldehyde]

Heh. If NASCAR went that route rubbing would certainly be racing.

By the next innovation, I assume you mean besides electrical and hydrogen-powered vehicles? I guess drive-by-wire technology isn't too far off, and so are vehicles that can drive themselves under most circumstances. Google already has a prototype that can do the latter.


Link to video.

There is an in-car video of the same run on Youtube, but it unfortunately has profanity so I can't post it.

The Google car running on an autocross course, as well as driving on the streets of San Francisco:


Link to video.

I wonder how it would compare to Mary Rice Pozzi.

 

[Quackers]

What do you think of F1?
I've learnt that drivers do very little and that the best machine wins the championship; which for me just feels wrong. Should we standardise F1 cars and put it up to the drivers to make up the difference?

 

[Formaldehyde]

I am a huge fan of F1. Check the sports forum for details.

No, the whole point of F1 is for the constructors to design and build cars that meet the rules. The constructors' championship is even far more important to many than the individual championship is. F1 is a huge industry that employs thousands of people. The budgets of the top teams are in the hundreds of millions of dollars. Much of that would disappear if it ever became a spec series.

There are plenty of spec racing series. While I would personally prefer to compete in one of those series myself, there is still far more than the vehicle that determines the winner. Car preparation and race strategy is quite frequently done by people other than the driver, not to mention the pit crew plays a very important role if it is not a sprint race. The driver is just one aspect to winning, albeit a critical one.