My Subaru has suddenly begun guzzling gas and we brought it in to our mechanic. He noticed that we had no oil left and that the turbo looked “cracked”. He said the turbo might be the cause. Have you ever heard of this problem with this particular car?
Subaru stopped selling the ‘XT’ in 1991. I know, because I always wanted one when I was young. Are you sure it is not a Legacy or Outback XT model?
Also, with turbo-charged engines, oil is extremely important. It not only lubricates the turbo, it keeps it cool. Checking the oil frequently and keeping the level up is the most important thing you need to do. Changing the oil on time every time is also just as important. Most late-model turbos specify using synthetic oil because it withstands the stress and heat produced by the turbo without coking or sludging up like standard dino oil can. This is not just about Subaru turbos, but turbos in general.
If the oil level were allowed to drop, the turbo is usually the first, and very expensive, casualty. If the turbo is bad, gas mileage can increase, since the engine was designed to run optimally with the extra boost from the turbo. Without that boost, the engine may not build enough compression to produce the power your used to, and you simply use more gas to get the car going.
I think that excessive gas consumption is the least of your worries at this point.
Unfortunately, Subaru Turbo-charged engines of that era are prone to problems if the oil is not changed every 4,000 miles/3 months. The buildup of sludge that results from longer oil change intervals leads to problems with lubrication of the turbocharger. These problems are also related to the Banjo Bolt in the turbo unit.
If your mechanic found “no oil left”, the main bearings, cylinder walls, and other friction surfaces in the engine are likely to have been extensively damaged. It may be time to start looking for a replacement engine for this car.
Does the vehicle(Forester was only XT in 04) still have the strong power as always or not more the extreme power it once did?
Any turbo vehicle can/will fail at turbocharger with low oil or elongated oil changes.
Subaru screwed up and specified 7500 miles on regular oil back in 2004-2006 on theirs turbos. This worked fine for WRX’s but it had a different motor(2.0L). The Forester, Outback, Legacy(2.5L) has early turbo failures and they highly recommended 3750 miles.