Don’t use Chevron or Exxon gas, the Vallejo service rep said two days before we were to leave on vacation. Their gas fouls the injectors.

What? I said in disbelief. Which gas should I use? When I stop in the middle of Nevada to buy gas, how do I know it’s okay?

He shook his head, resolutely sticking to his ridiculous advice.

As I explained last week (you can read the beginning of the story at www.CarquinezReview.com), we traded in our reliable Ford for a ’97 Chevy Blazer, named Ruby, so that we could tow a tent trailer through the southwest. Six weeks before we were to leave on vacation, right after we bought the car, we began having problems that were always signaled by the flashing of the Service-Engine-Soon light, his blinking yellow eye causing my chest to constrict, as he relentlessly blinked SOS, SOS, SOS, ominously announcing trouble.

I enviously watched Blazers, S10 pickups, and GMC Jimmys pass me on the highway—all three derive from the same roots—running just fine, wondering if SOS plagued them, if their injectors were clogged, or if they had somewhere found a pure gas capable of liberating them from clogged arteries.

At the first sign of trouble, days after we had bought Ruby, I had taken her to a Benicia mechanic who said that Blazers were notorious for injector problems. The dealer needed to replace them, he had said, and we’d be okay.

We took Ruby back to Vallejo more times than I can remember. We’d drop her off. They’d clean or otherwise muck with her injectors, telling us all was well. I’d take Ruby home. SOS would blink again. Ruby’s heart would beat irregularly.

After constant prodding, the Vallejo dealer finally replaced the injectors, and Ruby seemed well. But a few days later, after Ruby had been sitting in the Oakland Airport parking lot, she barely started and was running on only half her six cylinders. SOS blinked at me. Our problems had worsened.

Adverse selection posits that the uninformed buy used cars, thinking they’re good deals, because they don’t realize that most used cars are lemons. But I don’t believe in lemons. Cars are high-tolerance, mass-produced machines, and such machines can be fixed. If they couldn’t, dead cars would litter roadsides.

But who would fix Ruby and at what cost? The Vallejo work had been done free of charge under GM's safety warranty, but Ruby was sicker than ever. When the Vallejo rep blamed bad, evil gas, I got angry. I had had enough.

I took the car back to the Benicia mechanic. I waited in the lobby. He came out, saying that he had finally found my problem: the fuel filter was clogged. Ruby’s heart beat regularly and SOS had stopped. It was Friday night. We were elated.

While getting the tent trailer on Saturday, Ruby was parked on a slight incline as I fiddled with the hitch. I smelled gas. Looking underneath her, I saw gas streaming onto the asphalt, but it wasn’t coming from the fuel filter. Obviously, we weren’t going anywhere.

First thing Monday morning, Ruby was back at the Benicia mechanic’s. He found an incorrectly installed gas-tank fitting. Someone must have taken the tank down before, he said, perhaps to replace the fuel pump which sits in the tank. Oh, he said, the car’s misfiring again. Maybe your injectors are bad.

But the fuel filter? I said in disbelief. I thought the problem had been fixed!

He suggested I take Ruby back to the Vallejo dealer.

Which is the last thing I would do, even if my warranty required it. We drove instead to a Fairfield dealer. We breathlessly told him our sad story, fanning our ream of service papers. He shook his head compassionately. I asked him if there might be something in the gas. He said he’d check.

When we picked up the car, he was holding a small vial of gas sampled after the injectors. It was clean, he said, holding it up to the light. Where he saw clarity, I saw a dirty glass filled with a uric liquid.

He had replaced one injector and cleaned the others, he said. SOS was no longer blinking. The engine was running fine. I reminded him that we had followed this path many times before. Should we start our trip? I asked. He knowingly smiled and told us to have a good time. Relax, he said. I asked him what gas we should use. Chevron was the best, he said: We use their additive to clean the injectors.

We left that evening for Yosemite, where we camped for two nights. After stopping at Mono Lake, we drove to Las Vegas, hoping to camp at Lake Mead, but arrived late and stayed instead at a motel in Boulder City.

In the morning, Ruby wouldn’t start. The evil eye relentlessly blinked SOS, SOS, SOS….