Switched from PM to AG, why did my efficiency go up?

So I've been brewing partial mash batches for a while now, using DeathBrewer's approach except that I mash 6-7 lbs in a cooler rather than a kettle. With this approach I've been consistently hitting 70% efficiency, +/- 1%.

Last weekend I did my first AG batch, a cream ale that used 6 lbs 2-row, 1 lb minute rice and 0.5 lb table sugar. It's a 5-gallon batch, the estimated OG was 1.040 and I mashed for 90 minutes instead of my standard 60 minutes. My measured OG was 1.044, which beersmith calculates as 77% efficiency.

I've never brewed with rice or sugar before. This and the 90 minute boil are the only changes to my process. Grain crushed on the same mill, etc. Do you think the jump is because of the longer mash time, the rice/sugar, or just something random and not worth thinking about? I'm just trying to better understand the cause/effect of my process. Thanks.

Too many factors involved to give you a straight forward answer, especially since this was your first AG, if you continue to hit a higher efficiency as you move forward than you are doing great! If you start to lose that efficiency then we can help you try to diagnose the problem, if there happens to be one

yeah, it could be from any number of things.

However, the most significant thing appears to be the time. depending on how much you stirred during your previous mashes, the extra 30 minutes probably just aided in conversion efficiency, and boosted your overall extraction.

Thanks guys. I appreciate your input. I knew I was asking a somewhat impossible-to-answer-for-sure question but thought I'd ask for hunches. The extra 30 minutes seemed most likely to me. Next time I brew I'll try to change fewer variables to pin it down. Thanks again!

The best way we could help is with a simple recipe. Too many variable changes makes it almost impossible to say exactly what's happening. Try a couple more batches and see what happens. Then, if the "problem" persists, come back, and we can try to get that pesky efficiency back down into the low 70's, where it belongs.

The most important thing will be consistency. That will allow you to predict how your beer will come out based on the ingredients, process, and equipment used.

Thanks, and agreed. Right now I'm much more concerned with consistency and predictability than I am with my efficiency specifically.