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" Q: have an old SUV, a 1973 I.H. Scout II. The servicing manual tells me to change the gear oil every 6 months with &amp;quot;straight mineral oil SAE-90&amp;quot;. I keep thinking that a more modern oil would be better for my gears, require less frequent changes, and be a little easier to find at the store. However, I have been a little shy to make the switch since I am not sure if there is a reason for the &amp;quot;straight mineral oil&amp;quot; directed by the manual, or if that was just the best they had in 1973. Can I upgrade the oil in my transmission, transfer case, and differentials? If so, what would you recommend? Also, when making the switch to a different oil, do you recommend a procedure to ensure all the old stuff gets out, to prevent any mixing of the two types?  A: I&amp;#039;d just use a GL-4-rated 80W-90 mineral-based gear lube.  The 80W-part of that spec means slightly better performance at low temperatures until the tranny warms up. GL-4 is a specification for a gear oil intended for use in gearboxes, not in differentials with hypoid gears, which need much higher amounts of extreme-pressure lubricants. These EP lubricants are zinc-based, and can corrode some non-ferrous metals (like brass synchros and shift forks) used in transmissions. Just drain and refill\u2014no need to flush. Q: My son bought a second hand car. The first week it was working fine, but now there is a smell so bad that when the car is running I have to have my head against the opened window. He drove for 10 minutes and his hands became numb with pins and needles and all his nails looked like they had turned black. What is going on? A: DO NOT DRIVE THIS CAR, even with the windows open, until the exhaust leak is fixed.  Your son shows classic signs of carbon monoxide poisoning--Cyanotic nail beds and paresthesia in his extremeties. An immediate trip to the hospital emergency room is in order. CO poisoning can linger for months. The CO combines with hemoglobin in your red blood cells permanently, preventing those cells from carrying oxygen any longer. The hemoglobin stays tied up until that particular cell dies, usually around 3 weeks or so. Q: Does fuel injector cleaner take care of condensation in your car&amp;#039;s gas tank? A: Yes. But most gasoline in the US now has a substantial concentration of ethanol to meet emissions or non-renewable fuel requirements, so water contamination/condensation isn&amp;#039;t the issue it used to be. Q: New York State requires that gasoline sold in the state to have 10% ethanol. Does that change the fuel grade? A: Well, that alcohol does have an octane rating of over 110, and mixing it with lower-grade fuel will raise the anti-knock of the mixture. But you&amp;#039;re not mixing 87-octane fuel with gasoline yourself, which would give you a product with a rating of 89 or more. I assure you the anti-knock index printed on the pump is what&amp;#039;s coming out of the nozzle. Refineries will blend that mixture to the poorest, cheapest grade of fuel they&amp;#039;re allowed too. Q: I just bought a 1997 Volvo 850 station wagon, and I had $2,000 of work put into it. The R-134A in the a/c was a bit low, so my shop, which specializes in Volvos, said they couldn&amp;#039;t find any leaks, so they topped it off and put a fluorescent dye in the refrigerant. I just drove the car down to east L.A., where my wife is going to school. Very hot climate, unlike the San Francisco Bay where I bought it. Today, she came home and said the A/C had started blowing hot air. Then, when we tried to start the car, it didn&amp;#039;t have enough battery juice left to turn over. We jumpered it, started it, charged it, and when we turned on the A/C, we got about 10 seconds of cool air, then it went back to hot. So we turned off the A/C, and everything was fine. After about 20 minutes of driving, we tried the a/c again and got about 10 minutes of cool air before it started getting warm again -- essentially just the temperature outside. Here&amp;#039;s what I&amp;#039;m thinking. The Volvo 850 has an &amp;quot;automatic&amp;quot; a/c, which turns on and off as needed to reach a target temperature. Upon moving to east L.A., it&amp;#039;s way hotter out, so it&amp;#039;s working harder than it used to, which means it&amp;#039;s switched on more of the time, averaging a higher current draw. Maybe it&amp;#039;s a weak alternator. If the a/c were drawing more current than it&amp;#039;s designed for, it would blow a fuse. But I think the a/c is working properly and the alternator is just barely keeping up while it slowly draws down the battery. I suspect we&amp;#039;ve just barely avoided killing the engine on the highway by turning off the a/c when it stops being useful, at which point the alternator starts getting ahead and the battery starts charging again. Am I way off, or can you think of any other explanations for this problem? A: That still doesn&amp;#039;t explain why the a/c goes to hot within a few miles, does it? I&amp;#039;d take it back to the shop that worked on the a/c and find out what&amp;#039;s going on there. The electrical problem is something else. A charging system check is called for. You should see 13.5 to 14.5 volts across the battery posts at fast idle or while driving, maybe a half-volt less at idle. And that&amp;#039;s with the a/c on or not. "^^<http://www.w3.org/2001/XMLSchema#string>
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