Hello from Texas

[spil]

I've been lurking here for a while, and have been using a lot of the techniques here, but still have a lot of questions. I drive a 2000 Jetta with a 2L engine and manual transmission. I re-inflated my tires a few weeks ago to maximum tire pressure on the sidewall, and I'm wondering how often I should check/top off my tires. I coast down hills (in neutral, engine on), accelerate slowly, turn off the engine at long stoplights (15 seconds or more), never use the a/c or roll down the windows, and EOC down a little hill about a quarter mile from my house (very deserted, if I see another car approaching, I will leave the engine on).

I have a few questions on (hopefully) pretty basic stuff. My main question is if I am stopped at a red light with my engine off and my lights (either daytime or full lights) and radio turned on, do I have to worry about my battery dying, or does the small fraction of time my engine is off not make a big enough impact on the battery to not give it enough power to start? Also, do I have to worry about my starter not working because I turn it on and off so much (or at least a lot more than I used to)?

I'm thinking about getting a scanguage, but was wondering how much of a difference it would make in FE? If I was paying for my gas, I would definitely get one, but my parents pay for gas most of the time, so I have less incentive to buy one (at least for monetary reasons). I might just buy one and use it for a few weeks/months to find out the most effecient RPM's to shift at and then sell it. I think I read here that Scanguages sell on ebay for almost retail price?

Thanks for your input

[ptsmith24]

First off, welcome to the site.

It sounds like you have a good head start on some pretty good techniques. The scangauge would give you a good idea on acceleration techniques and the like and you may end up liking it too much to sell it. From what I understand, you could sell it for about what you pay for it. Personally, I have a 1990 vehicle which is not scangauge compatible. I am building the MPGuino, however, and hope to have that operational by this weekend sometime. As far as the battery dying, I don't think it would be enough pull on the battery to worry about killing it too much to start again (usually we're talking a minute or less of down time). Think about when people leave their headlights on all night. It isn't going to kill it in a matter of a minute (which is on the longer side that you'd leave your motor off anyway...at least in my experience, the longest I think it's off is maybe 30-45 seconds tops).

Look forward to your posts elsewhere

[cfg83]

spil -

Welcome to EM! Like ptsmith24 said, don't be surprised if you get attached to your ScanGauge. It has that effect on people.

I am thinking that you should check your tire pressure maybe once a week when the tires are cold. If there is a noticeable drop in pressure, then you may need to check more often. I also know that you need to use a reliable tire pressure gauge. Otherwise you may over-inflate the tires. I like to reference this website for all things tire (or tyre as they say in the UK) :

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

Lies, damn lies, and tyre pressure gauges.

Whilst on the subject of checking your tyres, you really ought to check the pressures once every couple of weeks too. Doing this does rather rely on you having, or having access to a working, accurate tyre pressure gauge. If you've got one of those free pencil-type gauges that car dealerships give away free, then I'll pop your bubble right now and tell you it's worth nothing. Same goes for the ones you find on a garage forecourt. Sure they'll fill the tyre with air, but they can be up to 20% out either way. Don't trust them. Only recently - since about 2003 - have I been able to trust digital gauges. Before that they were just junk - I had one which told me that the air in my garage was at 18psi with nothing attached to the valve. That's improved now and current-generation digital gauges are a lot more reliable. One thing to remember with digital gauges is to give them enough time to sample the pressure. If you pop it on and off, the reading will be low. Hold it on the valve cap for a few seconds and watch the display (if you can).

Generally speaking you should only trust a decent, branded pressure gauge that you can buy for a small outlay - $30 maybe - and keep it in your glove box. The best types are the ones housed in a brass casing with a radial display on the front and a pressure relief valve. I keep one in the car all the time and it's interesting to see how badly out the other cheaper or free ones are. My local garage forecourt has an in-line pressure gauge which over-reads by about 1.5psi. This means that if you rely on their gauge, your tyres are all 1.5psi short of their recommended inflation pressure. That's pretty bad. My local garage in England used to have one that under-read by nearly 6 psi, meaning everyone's tyres were rock-hard because they were 6psi over-inflated. I've yet to find one that matches my little calibrated gauge.

One reader pointed something else out to me. Realistically even a cheap pressure gauge is OK provided it is consistent. This is easy to check by taking three to five readings of the same tyre and confirming they are all the same, then confirming it reads (consistently) more for higher pressure and less for lower pressure.
One last note : if you're a motorcyclist, don't carry your pressure gauge in your pocket - if you come off, it will tear great chunks of flesh out of you as you careen down the road....

CarloSW2