At 90 amps, you are at the high-ish end of the recommended range for 3/32" 7018 electrodes, so if you could manage to turn the heat down a bit, you might blow through less.
With a little skill, a person should be able to run a 1/8" electrode on 1/8" material without blowing through. The travel speed will have to pick up, and the beads may be bigger and uglier than if a smaller electrode was used. But it can be done. So if you are blowing through 1/8" material with 3/32" rods, it is probably a matter of technique. In general, you should probably pick up your travel speed, but if you simply move your hand faster without learning to read the puddle, you're not going to get much better results. Unfortunately, reading the puddle isn't something that can be taught over the Internet. You just need hood time and to watch examples of people who know what they're doing. I will say, however, that I notice the puddle get a certain "saggy" look when it is about to blow through. That tells me that I need to pick up my travel speed immediately or, possibly, break the arc, let the metal cool, and come back to the joint then.
I have had problems blowing through 1/8" material with 1/8" 7018 when my fitup was poor. 7018 is not the best choice for filling gaps. It can be done, but it takes more skill. When I have tried to use 7018 with poor fitup and gaps, I have quickly blown through, because the heat gets concentrated at the edges of the two pieces that make up the joint.
For cases where there is a gap, a fast-freeze rod like 6011 is ideal. However, it takes some technique to use successfully and control the heat and deposition--unlike 7018, which you can kind of just drag along and it'll do fine. If you don't want to spend time learning to run 6011, you can continue to use 7018, just make sure your fitup is as good as can be, to minimize gaps. 6013 may also be a good choice. It has its own eccentricities in how you have to run it, but it is okay at filling gaps and can be run at a lower temperature than rods with iron powder in the flux like 7018 or 7014, so it may help you avoid blowing through.
