Si evitamos ese peaje, tardaremos más pero gastaremos menos gasolina.

In Spanish, after si (meaning if), you generally do not use the present subjunctive. For real or likely conditions, Spanish uses:

• Si + present indicative → future (or imperative, etc.)

So Si evitamos ese peaje, tardaremos... = If we avoid that toll, we will take longer...
Si evitemos is not used in standard Spanish.

This is the common “real future condition” pattern:

• Si + present indicative → result in the future

So:

• Si evitamos... (if we avoid...)
• tardaremos... / gastaremos... (we will take... / we will spend...)

It’s like English: If we do X, we will do Y.

They express different likelihood/attitude:

1) Si evitamos ese peaje, tardaremos...
A realistic possibility: If we avoid it (which we might), we’ll take longer.

2) Si evitáramos/evitásemos ese peaje, tardaríamos...
Hypothetical/less certain: If we avoided it, we would take longer.

So the second one usually pairs with the conditional (tardaríamos, gastaríamos).

Peaje means toll (a toll you pay on a toll road).
It’s masculine: el peaje, ese peaje.

Even though it ends in -e, grammatical gender is masculine here.

Spanish has three common demonstratives (in many Latin American varieties, this three-way distinction still exists in usage, though ese is very common):

• este = this (near me / the speaker)
• ese = that (near you / or not close to me; often the default “that”)
• aquel = that over there (far from both)

ese peaje = that toll (the one we’re talking about / not right here).

It’s normal to place a comma after an introductory si clause when it comes first:

• Si X, Y.

So: Si evitamos ese peaje, tardaremos más...
(English does the same: If..., ...)

Here tardar means to take (time) / to take longer.

• Tardaremos más = It will take us longer / We’ll take longer.

Tardar can relate to “being late” in some contexts, but in this structure (tardar + más/menos) it’s about duration.

• más (with accent) = more
• mas (no accent) = a formal/literary but (similar to pero)

So the accent distinguishes meanings.
menos only has one common meaning (less) and doesn’t need an accent.

Use pero when you’re contrasting two true ideas:

• We’ll take longer, but we’ll spend less gas. (Both can be true.)

Use sino after a negation to mean but rather:

• No iremos por la autopista, sino por la carretera. = We won’t go via the highway, but rather via the road.

This sentence isn’t structured that way, so pero is correct.

With quantities in Spanish, you typically say:

• más/menos + noun (no de)

So:

• menos gasolina = less gas
• más tiempo = more time

You might see menos de + number/amount with numerals:

• menos de 10 litros = less than 10 liters

No. Spanish usually drops the subject pronoun because the verb ending already shows it.

• evitamos, tardaremos, gastaremos clearly indicate we.

You could add nosotros for emphasis or contrast:

• Si nosotros evitamos ese peaje... = If we (as opposed to others) avoid that toll...

Mostly yes. Evitar commonly means:

• to avoid (a thing, a situation, a route)
• to prevent (something from happening), depending on context

Here it’s straightforward: avoid that toll = choose a route that doesn’t include it.